IAWA Journal, Vol. 26 (1), 2005: 1-68

WOOD ANATOMY OF THE SUBFAMILY EUPHORBIOIDEAE A comparison with subfamilies Crotonoideae and Acalyphoideae and the implications for the circumscription of the Euphorbiaceae

Alberta M. W. Mennega Nationaal Herbarium Nederland, Utrecht University branch, Heidelberglaan 2, 3584 es Utrecht, The Netherlands

SUMMARY

The wood anatomy was studied of 82 species from 34 out of 54 genera in the subfamily Euphorbioideae, covering all five tribes recognized in this subfamily. In general the woods show a great deal of similarity. They are charac­ terized by a relative paucity of vessels, often arranged in short to long, dumbbell-shaped or twin, radial multiples, and by medium-sized to large intervessel pits; fibres often have gelatinous walls; parenchyma apotracheal in short, wavy, narrow bands and diffuse-in-aggregates; mostly uni- or only locally biseriate rays, strongly heterocellular (except Hippomane, Hura and Pachystroma). Cell contents, either silica or crystals, or both together, are nearly always present and often useful in distinguishing between genera. Radiallaticifers were noticed in most genera, though they are scarce and difficult to trace. The laticifers are generally not surrounded by special cells, except in some genera of the subtribe Euphorbiinae where radiallaticifers are comparatively frequent and conspicuous. Three ofthe five tribes show a great deal of conformity in their anatomy. Stomatocalyceae, however, stand apart from the rest by the combination of the scarcity of vessels, and mostly biseriate, vertically fused and very tall rays. Within Euphorbieae the subtribe Euphorbiinae shows a greater vari­ ation than average, notably in vessel pitting, the frequent presence of two­ celled parenchyma strands, and in size and frequency of the laticifers. Data from surveys of the two other subfamilies of the uniovulate eu­ phorbs, Acalyphoideae and Crotonoideae are compared and their relation­ ships are discussed. The comparison of Euphorbioideae, Acalyphoideae, and Crotonoideae shows a great anatomical conforrnity with only a marked difference in the presence of laticifers: scarce in Acalyphoideae and Cro­ tonoideae but nearly always present and often frequent in Euphorbioideae. All in all, wood anatomy supports a narrower family concept of Euphor­ biaceae, inc1uding only Acalyphoideae, Crotonoideae, and Euphorbioideae, while exc1uding Phyllanthoideae and Oldfieldioideae, as has recently been advocated by several authors. In Table 2 (p. 6-7), informative features are summarized. Key words: Wood structure, Euphorbioideae, Acalyphoideae, Crotonoi­ deae, crystals, latex tubes, lysigenous cavities, silica.

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INTRODUCTION Ever since Prof. G.L. Webster aroused my interest in the wood structure ofthe diverse family of the Euphorbiaceae, I have been studying its wood anatomy on a worldwide scale, taking his concept of the family as a base (Webster 1975). He recognized five subfamilies: Phyllanthoideae and Oldfieldioideae comprising the biovulate genera, and Acalyphoideae, Crotonoideae, and Euphorbioideae comprising the uniovulate genera. Wood structure proved to be greatly variable in the biovulate subfamilies as appeared from studies ofPhyllanthoideae (Mennega 1987) and Oldfieldioideae (Hayden 1994), in contrast to the more uniform structure of the three uniovulate subfamilies. Of the latter, Acalyphoideae was studied by Hayden and Hayden (2000). Moreover, a wood atlas has been published recently of end-grain photographs at low magnification covering all subfamilies and roughly half of the total number of genera. This atlas is intended to aid hand-lens inspection (Westra & Koek-Noorman 2004). The present contribution completes the wood anatomical picture ofthe Euphorbiaceae by presenting an extensive treatment of the subfamily Euphorbioideae, and an overview of the Crotonoideae. This paper is an amended version of an unpublished contribution presented at the International conference on the Systematics of the Euphorbiaceae at the Missouri Botanical Garden, St. Louis, in 1989. That account was based on Webster's generic con­ cepts (1987). However, papers by H.-J. Esser (1994,2001) dealing with the tribe Hip­ pomaneae offered new concepts on generic delimitations within this tribe, the largest of the subfamily. Esser's concepts being in closer agreement with wood anatomical features than Webster's classification (1994), the tribe Hippomaneae is treated here following the work ofEsser. In Webster's treatment (1994) the tribe Hippomaneae com­ prises 19 genera in 3 subtribes, whereas Esser (1994) recognized 36 genera and no sub­ tribes. However, in the recent elaborate overview of the subfamily by Radcliffe-Smith (2001), wherein Esser treated the tribe Hippomaneae, the tribe is split into two subtribes: Carumbiinae and Hippomaninae.

MATERIAL AND METHODS

The 34 genera studied are listed in Table 1. Of a number of genera no wood was available. For the greater part this concerns shrubby and monotypic genera. For two of these, data were taken from literature. Neither wood nor data were available of the following genera: Adenopeltis, Anomo­ stachys, Bonania, Conosapium, Dendrocousinsia, Ditrysinia, Endadenium, Hamilcoa, Microstachys, Monadenia, Senefeldera, and Spegazziniophytum. Data of the wood samples studied are recorded under the generic descriptions. Genera are treated alphabetically according to tribes and subtribes. Most samples are backed by herbarium vouchers and deposited in the collection of the Wood Anatomy section of the Nationaal Herbarium Nederland, Utrecht University branch. Others were pro­ vided by other institutes, cited in accordance with Stern's Index Xylariorum 3 (1988). Microscopic slides and macerations were prepared in the usual way. All slides are deposited in Utrecht (Uw). Density data were only occasionally available, depending on the size of the wood specimen, or records in the literature.

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Table I. Genera of the subfamily Euphorbioideae of wh ich wood was examined. Classification according to Radc1iffe-Smith's Genera Euphorbiacearum (200 I).

Tribe 1. Stomatocalyceae (Müll. Arg.) G.L. Webster Subtribe Stomatocalycinae Pimelodendron Hassk. Plagiostyles Pierre Subtribe Hamilcoinae Nealchornea Huber

Tribe 2. Hippomaneae A. Juss.ex Bartl. Subtribe Carumbiinae Homalanthus A.Juss. Subtribe Hippomaninae Actinostemon Mart. ex Klotzsch Balakata Esser Colliguaja Molina Dendrothrix Esser Excoecaria L. Falconeria Royle Grimmeodendron Urb. Gymnanthes Sw. Hippomane L. MabeaAubl. Maprounea Aubl. Neoshirakia Esser Pleradenophora Esser Pseudosenefeldera Esser Rhodothyrsus Esser Sapium Jacq. Sclerocroton Hochst. Sebastiania Spreng. Senefelderopsis Steyerrn. Shirakiopsis Esser Spirostachys Sonder Stillingia Garden ex L. Triadica Lour.

Tribe 3. Pachystromateae (Pax & K.Hoffm.) Pax Pachystroma (Müll. Arg.) Pax

Tribe 4. Hureae Dumort. Hura L.

Tribe 5. Euphorbieae Blume Subtribe Anthosteminae Anthostema A. Juss. Dichostemma Pierre Subtribe Neoguillauminiinae Neoguillauminia Croizat Subtribe Euphorbiinae Chamaesyce Gray Elaeophorbia Stapf Euphorbia L. Pedilanthus Neck. ex Poit. Synadenium Boiss.

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SURVEY OF THE WOOD CHARACTERS OF THE SUBFAMILY - Table 2

Physical properties Most woods are of medium density, yellowish brown or cream-coloured, and mostly without distinction between heart- and sapwood. Hard, dark brown, often yellowish­ ly streaked heartwood is present in Gymnanthes lucida, Hippomane maneineIla, Spiro­ stachys africana and S. venenifera. Low-density wood occurs in Hura and Euphorbia.

Anatomical characters Growth rings - Nearly always present, but inconspicuous. Indicated by a few rows of radially compressed, sometimes thicker-walled latewood fibres. Vessels - Generally diffuse, but in Actinostemon, Gymnanthes p.p., Pseudosene­ jeldera and Rhodothyrsus a striking radial zonation of alternating strips with or devoid of vessels occurs (Fig. 8, 37). Usually the majority in radial multiples of 2 to 4, often dumbbell-shaped (Fig. 13) or in twin rows, also often in clusters. Frequency from few per sq. mm in Elaeophorbia, Hura, Sapium to numerous in species of Chamaesyce, Pseudosenejeldera, Spirostachys. For the greater part between 10-25 per sq. mm. Tan­ gential diameter very small to large, most frequently 100-200 f-lm; often rather vari­ able within a genus. Perforations almost exclusively simple, only in Maprounea part of the perforations scalariform. In juvenile wood of Euphorbia grandicornis Uhlarz and Kunschert (1976) noticed a rare scalariform perforation plate. Ray-vessel perforations (perforated ray cells) were observed in several genera (Fig. 35; see also Giraud 1983). Intervessel pitting generally alternate, the bordered pits 4-16 f-lm in tangential diameter, largest in Hura and Sapium. In Euphorbia from alternate to opposite and scalariform in the cactoid species. Vessel-ray pitting usually large, half-bordered, the shapes regular or variable. The pits in Euphorbia p.p. and in Hippomane are large, elongate to scalariform; pits of two types occur often in one cell. Thin-walled tyloses in species of Anthostema, Excoecaria, Hippomane, Hura, Mabea, Plagiostyles, Pseudosenejeldera, and Sapium. Dark resin in Spirostachys. Vascular tracheids occasionally present in all genera in the vessel clusters or in long radial vessel chains. Ground tissue - Composed of non-septate libriform fibres, with exception of oc­ casional septate fibres noticed in Euphorbia cotinifolia and in Senejelderopsis. Walls thin to moderately thin; diameter of lumen usually exceeding the wall thickness. Fibres with gelatinous walls largely or completely occluding the lumen occur in a great number of genera. These fibres are distributed irregularly in patches or, more often, in tangen­ tial bands; no relation has been found between the presence of such fibres and bending or leaning of the trees. In several genera (Balakata, Colliguaja, Homalanthus, Hura, Maprounea, Neoguillauminia, Pimelodendron papuanum, Sapium, Sebastiania and Senejelderopsis) cavities in the fibre walls are occasionally noticed (Fig. 33). This type of cavity and their origin was described by Dias-Lerne and Angyalossy-Alfonso (1998) for four species of Euphorbiaceae, including Sapium and Sebastiania. These authors renamed the cavities "intrusive cavities" instead of using the term "transpierced region" as introduced by Gomes et al. (1988). Fibre diameter mostly 16-25 f-lm; occasionally much wider; 30-40 f-lm in Anthostema, Balakata, Elaeophorbia, Homalanthus, Hura, Pimelodendron papuanum, Sapium and Synadenium. Mean length generally 500-900

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!Am; 380 !Am in Euphorbia tirucalli, up to 1300 !Am in several species of Sapium. Pits small, simple or minutely bordered, usually restricted to radial walls, and absent to in­ frequent in tangential walls. Fibre/vessellength ratio showing a wide range: from 1.2 in Rhodothyrsus to 2.4 in Hura, usually 1.40-1.80. Parenchyma - Axial parenchyma always present. Generally apotracheal, reticulate, in one or two cells wide bands, the bands often interrupted, irregular, more or less undulating, c. 6-9 per mm, diffuse and diffuse-in-aggregates parenchyma also often present. Paratracheal parenchyma, if present, scanty. Strands mostly 4-8-celled, in Acti­ nostemon, Euphorbia, Excoecaria and Hura 2-4-celled, with a preponderance of 2-celled strands in Euphorbia. Rhombic crystals occurring in several genera; silica only noticed in Balakata, and in Shirakiopsis virgata as small bodies. Rays - Predominantly uniseriate, occasionally biseriate, often uniseriates locally bi­ seriate over a short distance (Fig. 22). In Pimelodendron, Plagiostyles, Pseudosene­ jeldera nitida and Sclerocroton 2-3-seriate rays of common occurrence. Heterocellular with few exceptions, irregularly composed of few rows of procumbent cells mixed with rows of square and upright cells. In multiseriates the uniseriate margins composed of square and upright cells, often of unequal and variable height. Procumbent cells tending to be short radially, and axially relatively high; upright cells relatively short, usually barely twice as tall as wide. Vertically fused rays present, often over I mm high, even up to 3 mm high in Pimelodendron amboinicum. In Grimmeodendron and Hura rays exceptionally low, and almost homocellular. Width of uniseriates mostly 16-20 !Am, up to 30 !Am in some species of Sapium; multiseriates 30-70 !Am wide. Number mostly 14-18 (20) per mm, in most species of Sapium less than 10 per mm. Conspicuous inter­ cellular spaces common (Fig. 43, 60). Laticifers often present as very narrow, thin­ walled, non-articulated tubes, difficult to discem because they are generally not sur­ rounded by deviating cells (Fig. 5, 7). In all Euphorbia species but one, laticifers are prominent features, large canals surrounded by a cluster of small-sized secretory cells (Fig. 78, 81). Pedilanthus shows another type with the tube being enveloped by one or two large thin-walled cells (Fig. 83). Cell contents - Rhombic crystals and globular silica bodies frequently present and of diagnostic value. Generally either crystals or silica occurring in ray and/ or parenchyma cells. In the following genera or species, however, both crystals and silica bodies are present: Colliguaja, Dendrothrix, Gymnanthes p.p., Mabea occidentalis, Maprounea brasiliensis, Sclerocroton schmitzii, Sebastiania klotzschiana, Senejelderopsis; gener­ ally in different tissues but sometimes in the same tissue. Crystals are solitary or paired in chambered ray or parenchyma cells, mostly in one type of tissue but in Nealchornea and Pimelodendron of Stomatocalycinae, and in Hippomane and Spirostachys of Hip­ pomaninae crystals are present in rays as weH as in parenchyma. In Hura crystals occur in non-chambered as weH as in chambered parenchyma cells. Cells containing several crystals of various sizes and shapes observed in Colliguaja, Hippomane, Hura, Neoguil­ lauminia and Pleradenophora. In the tribe Euphorbieae crystals seldom noticed, except in Neoguillauminia where they are frequent in ray cells; otherwise crystals noticed only in parenchyma of Dichostemma and in a sampie of Euphorbia balsamifera. Silica is restricted to the Hippomaninae, and, with exception of Balakata, occurs only in ray ceHs. In a number of genera, Actinostemon, Gymnanthes p.p., Pseudosenejeldera,

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Table 2. Selected characters in Euphorbioideae. - x = present; (x) = scarce; sc = scalariforrn; Par. = parenchyma; Lc =lysigenous cavities; pp = in part of the species. continued -+

Vessels number diameter element pits length Taxa studied [ e Ne e e ::!. e 0 e e ::!. = Ne Ne ::!. 8 ::!. [ 8 ::!. e ::!. 23 N 00 ::!. -0 1;l'" ].~ N 23 I 8 I 8 0 S I N § on 00 r- ~ 8 I "i :1 ..s ] 2 V :=: A V § A v on A ..". 00 0 Tribe Stomatocalyceae subtribe Stomatocalycinae Pimelodendron x x x x x Plagiostyles x x x x x subtribe HamiIcoinae Nealchornea x x x x x Tribe Hippomaneae subtribe Carumbiinae Homalanthus x x x x x x x (x) subtribe Hippomaninae Actinostemon x x x x x x Balakata x x x x Colliguaja x x (x) x x Dendrothrix x x x x Excoecaria x x x x x x Falconeria x x x x Grimmeodendron x ? ? ? x Gymnanthes pp x x x x x x x Hippomane x x x x x Mabea x x x x (x) x x (x) x Maprounea x x x x x x Neoshirakia x x x Pleradenophora x x x x Pseudosenejeldera x x x x x x x Rhodothyrsus x x x x x x Sapium x x (x) x x Sclerocroton x x x x x x Sebastiania x x x x Senejelderopsis x x x x Shirakiopsis x x x x x Spirostachys x x x x Stillingia x x x x Triadica x x x x x Tribe Pachystromateae Pachystroma x x ? x x TribeHureae Hura x x (x) x x x Tribe Euphorbieae subtribe Anthosteminae Anthostema x x x x x x Dichostemma x x x x subtribe Neoguillauminiinae Neoguillauminia x x x x x subtribe Euphorbiinae Chamaesyce x x x x x Elaeophorbia x x x sc Euphorbia x x (x) x x (x) sc Pedilanthus x x x sc Synadenium x x x sc

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I) Vessel-ray pits more or less similar to intervessel pits but half-bordered and sometimes slightly smaller or larger. 2) Vessel-ray pils different from intervessel pits by more irregular shapes and sizes and often with strongly reduced borders (see description).

Fibres Rays Par. Lc

diam. length F/V

Taxa studied E "- a -S E :§ cCI) E "- ~ E E 'e ~ ~ .2 "- ..,!l "- "- 0 ~ g "0 :::: R os '§ "§ "0 0 1 § ~ 'ü c ?'l a\ 0 M "E 1;l ~ 0 .s. .;l 6 6 v '"" v a\ " l .c .2 Co ~ u ~ u ~ Tribe Stornatocalyceae subtribe Stomatocalycinae Pimelodendron x x 1.50 x x x x x x x 4-8 Plagiostyles x x 1.80 x x x x 4-8 subtribe Hamilcoinae Nealchornea x x 1.54 x x x x x 4-8

Tribe Hippornaneae subtribe Carumbiinae Homalanthus x x 1.38 x x x x x 4-6 subtribe Hippomaninae Actinostemon x x 1.50 x x x x 4-8 Balakata x x 1.86 x x x x 4-10 Colliguaja x 1.67 x x x x 2-6 Dendrothrix x 1.37 x x x 4-8 Excoecaria x x 1.47 x x x 6-8 Falconeria x x 1.51 x x x 4-8 Grimmeodendron x x x x 4-9 Gymnanthes x x 1.60 x? x x x x 2-8 Hippomane x x 1.60 (x) x x x x 4-8 Mabea x x x 1.65 x x x x x 4-8 x Maprounea x x 1.53 x x (x) (x) 4-10 Neoshirakia x x 1.67 x x 4-8 Pleradenophora x 1.71 x x 4-8 Pseudosenejeldera x x 1.26 x x x (x) 4-8 Rhodothyrsus x x 1.22 x x x 4-8 x Sapium x x 1.58 (x) x x x 2-8 x Sclerocroton x x 1.74 x x x (x) 4-6 Sebastiania x x 1.46 x x 3-8 Senejelderopsis x x 1.30 x x x x 2-6 x Shirakiopsis x x 1.68 x x x (x) 4-8 Spirostachys x x 1.80 x (x) x 4-8 Stillingia x x 2.10 (x) x x 2-4 Triadica x x 1.65 x x (x) x (x) 4-8

Tribe Pachystrornateae Pachystroma ? ? x x

TribeHureae Hura x x 2.44 (x) x x 2-4

Tribe Euphorbieae subtribe Anthosteminae Anthostema x x 1.98 x x 4-8 x Dichostemma x x 1.55 (x) x x (x) x 2-8 subtribe Neoguillauminiinae Neoguillauminia x x 1.60 x x (x) 2-6 subtribe Euphorbiinae Chamaesyce x x 1.57 x x x 2-4 Elaeophorbia x 1.66 x x 1-4 Euphorbia x x x 1.92 x x (x) x 1-4 x Pedilanthus x x 2.00 x x 2-4 Synadenium x x 1.77 ? x 2-3

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Rhodothyrsus, Sclerocroton and Shirakiopsis, silica is present as unusually large bodies about 40 f,lm wide, completely filling the celliumen (Fig, 9), In Balakata, Colliguaja, Gymnanthes schottiana, Mabea, Maprounea p,p" and Senejelderopsis the silica bodies are small, c, 10-20 f,lm in diameter, Lysigenous cavities - Large radial cavities extending from the cambium into the wood, clearly different from laticifers by their size and position, were noticed in a num­ ber of genera of Euphorbieae, and in Mabea, Rhodothyrsus, Sapium, and Senejelder­ opsis, Record (1925, 1944) described these cavities as latex traces for several genera of Euphorbiaceae: Euphorbia, Mabea, Sapium, and indicated not to be able to determine the significance of these structures, Later suggestions of such cavities representing leaf traces, or even possibly latex canals, have not been substantiated. Chalk in Metcalfe and Chalk (1983) mentioned the occurrence of lysigenous cavities without true epithelium in some families, e.g. Euphorbiaceae, without further comments on their origin or function. Hayden and Hayden (2000) in their treatment of the subfamily Acalyphoi­ deae gave ample attention to the cavities recorded in several genera. They considered their presence as a diagnostic feature to support Alchomeae as a distinct tribe of the subfamily. These authors were also convinced that the cavities bore no relation to leaf traces - a conclusion with wh ich I concur since their position as seen on the surface of the sterns is far too irregular.

GENERIC DESCRIPTIONS

Tribe 1. STOMATOCALYCEAE (Muell. Arg.) G. L. Webster This tribe comprises four genera: Pimelodendron (syn. Stomatocalyx), Plagiostyles, Hamilcoa and Nealchornea. No wood was available of Hamilcoa. The three genera investigated are rather similar in wood structure, having few, medium-sized vessels, large intervessel pits, large elliptic vessel-ray pits, fibres of medium length (c. 1500 f,lm), and high, often biseriate, vertically-fused rays. Laticifers are present as narrow thin-walled tubes (10-20 f,lm wide) often difficult to trace due to not being enveloped by special cells. The main difference is found in ray size and cell contents. In Plagiostyles no cell contents were noticed, but Normand and Paquis (1976) reported the presence of crystals in the parenchyma. In the two other genera large rhombic crystals occur in both ray and parenchyma cells, often in chambered cells. In Nealchornea rays are exclusively uniseriate; however, their composition of procumbent, square and upright cells is the same as in the other genera with uni- and biseriate rays.

Pimelodendron Hasskarl - Fig. 4, 5 A genus of 6-8 species in Malaysia, Indonesia, Papua New Guinea and tropical Aus­ tralia.

Material studied: P. amboinicum Hassk. (syn. P. papuanum Warb.): Indonesia, Irian Jaya: BW 1395, BW 1477, BW 12316, Fokkinga 4137,4545; Java: BW 2686; Papua

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New Guinea: Dept. Für. 51 - P. griffithianum (Muell. Arg.) Benth. (syn. P. papaveroides J.J. Srnith): Sumatra: (WIBw 3762); Malaysia: Og-B364.

~ i' ... '" t=i ~ Dr..~~ ~Ii :-, .1. ~ "'I. 1 i.' ~ ,",~~1 j ,: ~ ~ ""- ~ fl' ~ I ~ ,'~;O: ~ ~ Li ~ ~ t~ ~ ~~ L' E: ~~ h ~ !!' ~ H~ ~ ~ ~ l:::l ""t-< '"'~ ~ ... EI ~ H ~ ~ "1 I;I;~ J l'II::!i! iI~ ~ ,WD :fl ~ - t ~ ~~liSl f :t\ ~if It ~ ~ J:Iii ' ~~

Fig. 1-5. Tribe Stomatocalyceae. - 1 & 2. Nealchornea japurensis, Krukoff 5278. - 1: Trans­ verse sec ti on showing radial vessel multiples and apotracheal parenchyma. - 2: Tangential sec ti on with strongly heterogeneous rays and large, slightly irregular vessel-ray pitting. - 3. Plagiostyles africana, Dechamps 63. Tangential seetion showing heterogeneous, often vertically fused rays and intervascular pitting. - 4 & 5. Pimelodendron amboinicum (syn. P. papuanum), Fokkinga 4137. - 4: Radial seetion, large vessel-ray pitting. - 5: Radial seetion, with latex tube (arrowheads), and parenchyma with crystals in chambered cells. - Scale bars: 1-3 = 100 !-lm; 4&5 =40 !-lm.

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Generalfeatures: Trees. Wood without distinction between heart- and sapwood. Colour creamish in P. amboinicum, creamish with a brown tinge in P. griffithianum. Texture fine, straight-grained; light; density about 0.50.

Microscopic features: Growth rings faintly indicated by a boundary of a few rows of radially compressed fibres. Vessels 20-50% solitary, remainder in radial multiples of 2-6, in twin rows and in clusters, diffuse, with a slight indication of radial arrangement, 5 (1-17) per sq. mm. Outline oval to round, diameter 80-170 f-lm; vessel element length 975 (825-1320) f-lm. Perforations simple; intervessel pits alternate, polygonal, large, 10-12(-16) f-lm; vessel­ ray pits large, round, oval or irregular, with strongly reduced borders. Fibres non-septate, diameter 20-25 f-lm, walls thin, 3 f-lm; intrusive cavities occasion­ ally present. Minutely bordered pits restricted to radial walls. Length 1450 (1000-1800) f-lm. F/V ratio 1.50. Rays uni - and biseriate, occasionall y triseriate; 15 -17 per mm. U niseriates composed either exclusively of upright and square cells or like in the multiseriates also some rows of procumbent cells present. In both types rays often vertically fused. Height up to 3 mm, multiseriate layers 100-500 f-lm high, the extensions often very long; width 16-30 f-lm. Intercellular spaces present. Laticifers c. 20 f-lm wide, noticed in all specimens. Perforated ray cells present. Large rhombic crystals occasionally present. Parenchyma mostly apotracheal, in one- to two-cell-wide, slightly wavy, often inter­ rupted bands, also diffuse as isolated strands; about 9 bands per mm. Strands of 4-8 cells. Large rhombic crystals present, often in chambered cells.

Note: The occurrence of laticifers in the rays of P. amboinicum as described by Sudo and Fujii (1987) could be confirmed. In material of P. griffithianum Ogata and Kalat (1997) did not find latex tubes, in contrast to my own observations. The wood structure of Blumeodendron, belonging to the subfamily Acalyphoideae, closely resembles that of Pimelodendron. Wood specimens of the two genera are occasionally mixed up, but can be distinguished by the absence of laticifers in Blumeodendron.

Plagiostyles Pierre - Fig. 3 A monotypic genus of tropical Africa.

Material studied: P. ajricana (Muel!. Arg.) Prain: Zaire-P: Dechamps 63 (Tw 8083); E. Africa: Zenker 1730 (RHw).

Generalfeatures: Medium-sized trees with a whitish, moderately hard wood.

Microscopic features: Growth rings faint. Vessels about 27% solitary, remainder in radial multiples of 2-4 or in clusters, dif­ fuse; 8 (3-16) per sq.mm. Outline oval to round, diameter 70-120 f-lm, vessel element length 650 (400-980) f-lm. Perforations simple, intervessel pits alternate, polygonal, 10-12 f-lm, vessel-ray pits large, irregular, borders slightly reduced. Thin-walled tyloses occasionally present, sometimes with crystals.

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Fibres non-septate, diameter c. 18 f-lm, walls 4-5 f-lm thick, numerous small pits with aminute border restricted to the radial walls; length 1170 (800-1420) f-lm. F IV ratio 1.80. Rays uni- and biseriate, 19 per mm. Uniseriates either composed of exclusively tall upright and square cells, or composed of a central part of procumbent cells bordered by short to long extensions of square and upright cells. The biseriates resemble the latter type of uniseriates except for the procumbent portion being two cells wide; both types often vertically fused. Height up to 1.8 mm (the part with procumbent cells from 6-18 cells, 320 f-lm high); width of biseriates 24-30 f-lm. Laticifers numerous. Parenchyma apotracheal in one-cell-wide, often interrupted, slightly wavy bands, and in isolated strands; number of bands c. 12 per mm. Strands of 4-8 cells.

Note: Normand and Paquis (1976) reported the presence of crystals in the paren­ chyma.

Nealchornea Huber - Fig. 1,2 A genus of 2 species in tropical South America.

Material studied: N.japurensis Huber: Brazil, Amazonas: Krukoff 4885,4967,5278, 8099 - N. stipitata Wallnöfer: Brazil, Amazonas: Krukoff 6358.

Generalfeatures: Colour yellowish brown, no distinction between heart- and sapwood. Texture rather fine, straight-grained; density c. 0.70.

Microscopicfeatures: Growth rings faint, boundaries formed by 4-6 rows ofradially compressed fibres. Vessels about 35% solitary, remainder in radial multiples of 2-6 or in clusters, dif­ fuse; 7 (2-20) per sq. mm. Outline round, diameter 120-150 f-lm; vessel element length 1000 (950-1050) f-lm. Perforations simple, lateral perforations often also present; inter­ vessel pits alternate, roundish, 10-12(-16) f-lm, vessel-ray pits large, somewhat irregu­ larly shaped, mostly more or less oval and horizontal, borders somewhat reduced. Thin­ walled tyloses occasionally present. Fibres non-septate, 24-28 f-lm wide, walls 4-6 f-lm thick, the lumen often occluded by a gelatinous layer, small pits with aminute border restricted to the radial walls. Length 1500 (1200-1780) f-lm. F IV ratio 1. 50. Rays uniseriate, seldom locally biseriate, more often so in N. stipitata; 13-17 per mm. Composed either exclusively of upright cells or with a short central part of procumbent cells (but higher in N. stipitata) and long extensions of variable length of square and upright cells, vertically fused rays also often present. Width 20 f-lm, height up to 2000 f-lm. Rhombic crystals seldom present in square and upright cells. Occasionally a nar­ row, thin-walled laticifer present. Intercellular spaces rather conspicuous. Parenchyma apotracheal in one-cell-wide, slightly wavy, often interrupted bands, 3-4 per mm. Strands of 4-8 cells. Rhombic crystals frequent, often in chambered cells.

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Tribe 2. HIPPOMANEAE A. Juss. ex Bartl.

According to Esser (2001) this tribe, the largest of the subfarnily according to the num­ ber of genera, consists of two subtribes: Carumbiinae and Hippomaninae. The first com­ prises only the genus Homalanthus, the other accommodates 33 genera, of which 23 were represented by wood sampIes, and one - Grimmeodendron - by a description by Carreras and Vales (1986). In general the anatomy is rather uniform, though some genera or groups of genera stand out by special features, like vessel distribution, occurrence of crystals and silica, and size and positions of vessel-ray pits, as mentioned in the discussion. The structure of Homalanthus resembles that of Sapium. Esser 's (1994, 2001) generic concept is nearly always in accordance with the anatorni­ cal structure, except in Gymnanthes, in which the investigated species show a remark­ able diversity in pit sizes, ray structure and cell contents.

Homalanthus A. Juss. - Fig. 6, 7 A genus of about 22 species occurring in the Old World from the Pacific Islands to Australia, Malaysia, southern Taiwan.

Material studied: H. arfakiensis Hutch.: New Guinea: Vink 17460 (Lw) - H.fastuosus (Linden) Fern.-Vill.: Philippines: Jacobs 7195, 7280 (Lw) - H. macradenius Pax & K. Hoffrn.: Philippines, Quezon: FPRI 587 - H. populneus (Geiseler) Pax: Philippines: J.P. Rojo (Tw 31613), a doubtful specimen (see note).

General features: Shrubs or trees. Wood without distinction between sapwood and heartwood, light yellowish brown, moderately fine-textured, fairly light; density 0.44.

Microscopic features: Growth rings hardly noticeable. Vessels diffuse, 30-50% solitary, remainder in radial multiples of 2-4(-6), few in clusters; 6 (2-14) per sq. mm. Outline oval, diameter 100-150 11m, vessel element length 1076 (750-1500) 11m. Perforations simple, with wide rims, intervessel pits alternate, polygonal, large, 12-15 11m; vessel-ray pits crowded, oval, ofthe same size as the inter­ vessel pits or larger, with strongly reduced borders. Fibres non-septate, very thin-walled, walls 2-3 11m thick, occasionally gelatinous over large areas, diameter usually about 24 11m, but up to 36 11m in H. macradenius and H. nutans (Detienne & Jacquet 1999), intrusive cavities rare. Pits small and simple, restricted to radial walls. Length 1535 (1250-2000) 11m. FIV ratio 1.43. Rays uniseriate, occasionally over a short distance biseriate; 10-14 per mm. Com­ posed of very irregularly distributed procumbent, square and upright cells, with a pre­ ponderance of square and short procumbent cells in H. macradenius; occasionally with long extensions of upright cells on one side. Vertically fused rays frequently present. Upright cells 80-160 !lm high. Width 20-24 11m, height up to 40 cells (2 mm). Inter­ cellular spaces prominent. Laticifers present. Bars of Sanio noticed in H. arfakiensis. Crystals scarce, occasionally present in chambered ray cells.

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Parenchyrna apotracheal in short, irregular, one-cell-wide bands and diffuse-in-ag­ gregates. Nurnber of bands 4-7 per rnrn. Strands of 4-8 cells.

Fig. 6-10. Tribe Hippomaneae. - 6 & 7. Homalanthus. - 6: H. arfakiensis, Vink 17460. Trans­ verse section showing reticulate parenchyma. -7: H. macradenius, FPRI 587. Tangential sec­ tion showing uniseriate rays, one with latex tube (arrowheads). - 8-10. Actinostemon. - 8: A. lundianus, Krukoff 5551. Transverse section showing the vessel arrangement in radial strips. - 9: A. schomburgkii, Schulz 10061. Radial section, ray cells filled with large silica lumps. - 10: A. concolor, Lindeman & H. de Haas 1310. Tangential section; note rays with scarce procum­ be nt cells. - Scale bars: 6 = 250 !-lm; 7 & 9 =40 !-lm; 8 & 10 = 100 !-lm.

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Note: The most common species, H. populneus, alas, is represented only by a speci­ men collected by Rojo in the Philippines (Tw 31613), and differing in so many respects from the other species that I feel justified to consider it as rnisidentified. The more so while a description by Janssonius (in Moll & Janssonius 1934: p. 789-798) of a wood sampie of H. populneus collected in Java (Koorders 2160) is in perfect accordance with the general pattern given above. The same is true for adescription by Janssonius of a specimen of H. giganteus wh ich was not seen by me. This specimen also was collected by Koorders in Java (2030). Homalanthus nutans Guill. from Polynesia as described by Detienne and Jacquet (1999) fits quite weIl, apart from shorter vessel elements and fibres, as compared to the material seen by me. Pax and Hoffmann (1912) placed Homalanthus with Pimelodendron in the subtribe Carumbiinae. This subtribe was recognized by Webster (1994), though he excluded Pimelodendron. Esser, in his revision of Homalanthus (1997), agreed on the isolated position of that genus in the Hippomaneae. Consequently the subtribe Carumbiinae was maintained (Esser 2001). Anatornically , however, Homalanthus fits so weIl in the subtribe Hippomaninae that a subtribe of its own is not supported by wood anatomy.

Actinostemon Mart. ex Klotzsch - Fig. 8-10 A genus of about 15 species in the West Indies and South America.

Material studied: A. amazonicus Pax & K. Hoffrn.: Brazil, Rio Purus: Prance et al. 13992; Rondonia: P. Maas 385 - A. concolor (Spreng.) Muell. Arg.: Brazil, Santa Catarina: Reitz 22181; Parana: Lindeman & H. de Haas 911, 1310 - A. lundianus (Didr.) Pax: Brazil, Rio Purus: Krukoff 5551 - A. schomburgkii (Klotzseh) Hochr.: Suriname: Schulz 10061.

Generalfeatures: Small trees with a fine textured yellow wood without differentiation in heart- and sapwood; cross section with a radial zonation when seen through a hand­ lens, giving the illusion of wide rays. The wood is hard and heavy.

Microscopic features: Growth rings rather conspicuous, boundaries formed by 1-3 rows of radially compressed thick-walled fibres. Vessels 25% solitary, remainder in radial multiples of 2-6, occasionally in twin mul­ tiples; distribution in radial zones alternating with zones without vessels, except in A. concolor; 40 (36-45) per sq. mm. Outline oval, diameter 30-60 !lm, walls rather thick; length of vessel elements 583 (500-636) !lm. Perforations simple, intervessel pits alter-nate, polygonal, 4-6 !lm, or slightly larger; vessel-ray pits similar, crowded. Fibres non-septate, diameter 12-20 !lm, walls 2-4 !lm, partly gelatinous, pits numer­ ous, very small with minute borders, restricted to radial walls. Length 853 (802-880) !lm. FIV ratios 1.5 (1.3-1.73). Rays uni- and biseriate; 12-20 per mm. Uniseriates in two types, one type composed exclusively of upright cells, the other type heterocellular, the central part consisting of relatively short and high procumbent cells, the margins of rows of upright and square cells; biseriate rays resembling the second type of uniseriate rays, except for being

Downloaded from Brill.com10/09/2021 12:24:23AM via free access Mennega - Wood anatomy of the Euphorbioideae (Euphorbiaceae) 15 double over a height of 2-5 rows of cells, the uniseriate margins very high. Width 18-22 ~m, height ofuniseriate rays up to 800 ~m, biseriates up to 2 mm. Perforated ray cells occasionally present. Laticifers observed in A. concolor and in A. schomburgkii. Tangential zones of rays with silica altemating with zones of rays without silica. The large silica bodies almost completely filling the lumen of most procumbent cells. Parenchyma apotracheal, diffuse-in-aggregates and in few to numerous, short, one­ cell-wide bands, about 9 per mm. Strands of 4 (8) cells.

Note: Webster in arecent publication (1994) considered Actinostemon conspecific with Gymnanthes. In his opinion no satisfactory differentiating characters exist between the two genera. Sebastiania is also mentioned (Webster & Huft 1988) as a genus difficult to distinguish from Gymnanthes s.l., although it is not considered as a synonym. The anatomy of the wood does not entirely favour incorporating Actinostemon in Gymnan­ thes. On the other hand, the radial vessel zones characteristic for Actinostemon also occur in PseudoseneJeldera, formerly inc1uded in SeneJeldera, a taxon considered by Jablonski (1969) to fit in an evolutionary trend SeneJeldera-Gymnanthes-Actinostemon. See also the notes under Gymnanthes and PseudoseneJeldera.

Balakata Esser - Fig. 11,12 A genus of 2 species in East Asia, Indonesia and the Philippines.

Material studied: B. baccata (Roxb.) Esser: W. Pakistan: Matundar & Islam (Tw 25181); Thailand: van Beusekom 373 (Lw); N. Sumatra: de Wilde & de Wilde-Duyfjes 12838 (Lw); Indonesia: LEw s.n., WIBw 3789, 3790 - B. luzonica (S.Vidal) Esser: Philip­ pines: Bur. of Forestry 17801 (Tw 47507), Laguna, EP.R.I. 209.

GeneralJeatures: Large trees. Wood yellowish brown without differentiation in heart­ and sapwood, light and soft.

Microscopic features: Growth rings inconspicuous. Vessels diffuse, 20-40% solitary, remainder in radial multiples of 2-5(-8); 2-4 (0-8) per sq. mm. Outline oval, diameter variable from 150-320 ~m, length ofvessel elements 970 (700-1300) ~m. Perforations simple, intervessel pits large, crowded, 10-16 ~m, oval to polygonal, vessel-ray pits similar or larger and irregular, with strongly re­ duced borders. Fibres non-septate, diameter about 25 ~m, occasionally wider, walls thin, c. 3 ~m, part of the fibres with gelatinous walls, intrusive cavities present. Pits few, small, re­ stricted to radial walls. Length 1600 (1250-1925) ~m. F/V ratio 1.72 (1.48-1.87). Rays uniseriate in B. baccata, partly biseriate in B. luzonica; 10-14 per mm. Com­ posed of square cells intermingled with procumbent cells of the same height, and with rather low upright cells. Width 16-20 ~m, up to 40 ~m in biseriates, height usually 400-900 ~m, occasionally up to 1400 ~m, vertically fused rays of B. luzonica up to 3000 ~m (44 cells). Medium-sized silica bodies (10-20 ~m) almost always present in cells of all types; rhombic crystals occurring sporadically in B. luzonica. Occasionally narrow laticifers present.

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Parenchyma apotracheal in irregular, often interrupted, narrow, one- to two-cell-wide bands, occasionally the bands more continuous. Strands of 4-8 cells. Silica bodies either absent or sporadically present in B. baccata to frequently present in B. luzonica.

Fig. 11-15. Tribe Hippomaneae. - 11 & 12. Balakata baccata. - 11: de Wilde & de Wilde­ Duyfjes 12838. Transverse seetion, most !ibres with gelatinous inner layer. - 12: Tangential seetion, with uniseriate rays. - 13-15. Colliguaja brasiliensis, LEw 4489. - 13: Transverse seetion with radial vessel rows, one dumbbell-shaped. - 14: Radial seetion showing vessel-ray pits of variable sizes with reduced borders. - 15: Tangential seetion, intervessel pits. - Scale bars: 11 = 65 !Am; 12 = 100 !Am; 13 = 250 !Am; 14 & 15 = 35 !Am.

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Note: Kruijt (1989,1996) excluded Sapium baccatum from the genus and transferred it to Excoecaria. In 1997 Esser et al. treated the taxon as "unnamed genus I" (UG 1), standing apart from Sapium as weil as Excoecaria. Shortly afterwards Esser (1999b) created the genus Balakata, transferring the species Sapium baccatum and S. luzonicum to it. Sapium merrillianum was brought into synonymy with Balakata luzonica. The new genus is distinguished from Excoecaria, as weil as from Sapium, by the presence of silica bodies.

Colliguaja Molina - Fig. 13-15 A genus of 4 species (Esser 2001), restricted to the southem part of South Amer­ ica.

Material studied: C. brasiliensis Klotzsch: Argentine: (LEw 4489). Generalfeatures: Shrubs, with rather coarse, moderately hard, light brown wood.

Microscopic features: Growth rings hardly noticeable. Vessels diffuse, seldom solitary, for over 95% in radial multiples of 2-8, often in twin rows or in dumbbell-shaped rows; 7 (2-17) per sq. mm. Outline oval, diameter 150 (50-240) !-lm, vessel element length 620 (460-720) !-lm. Perforations simple, in­ tervessel pits large, polygonal, 12-15 !-lm wide; vessel-ray pits irregular, large, often elongate or kidney-shaped, strongly reduced borders. Fibres non-septate, diameter 20-25 !-lm, walls thin, c. 2 !-lm wide, intrusive cavities noticed. Pits numerous, with small circular borders, restricted to radial walls. Length 1030 (700-1300) !-lm. FIV ratio 1.67. Occasionally one or two elongate crystals pres­ ent. Rays uni- and locally biseriate; 12.5 (11-15) per mm. Mainly composed of square cells, but rather tall and radially short, procumbent cells as well as upright cells, twice as tall as wide, also present. Height variable from 200-1100 !-lm, width 30-50 !-lm. Some rays with narrow laticifers. Rhombic crystals numerous, large and solitary or several of different sizes in a cell; occasionally in chambered cells. Small silica bodies (c. 4 !-lm) infrequently present. Parenchyma apotracheal, diffuse and in often interrupted narrow bands, 6-10 per mm. Strands of (2-)4-6 cells. Cells occasionally septate.

Dendrothrix Esser - Fig. 16 A genus of 3 species restricted to northem South America.

Material studied: D. yutajensis (lab!.) Esser: Venezuela: Maguire et al. 42212 (Tw 36524), Liesner 16685. Both sampies are twigs, 0.5 cm in diameter.

Generalfeatures: Low trees, up to 10 m.

Microscopic features: Growth rings very vague or absent. Vessels diffuse, about 21 % solitary, the remainder in radial multiples of 2-8, often also in twin rows or in clusters; 44 (31-53) per sq. mm. Outline oval, diameter 50-80 !-lm,

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Fig. 16-20. Tribe Hippomaneae. - 16. Dendrothrix yutajensis, Maguire et al. 42212. Transverse seetion with few solitary vessels and indistinct parenchyma. - 17 & 18. Excoecaria agallocha, Tw 22536. - 17: Transverse seetion showing margin of growth ring of radially flattened fibres. - 18: Radial section with large crystals in ray cells. - 19 & 20. Falconeria insignis, Tw 45179. - 19: Tangential section; parenchyma with numerous crystals, arrowheads indicating laticifer in ray. - 20: Transverse seetion showing reticulate parenchyma in one cell wide bands. - Scale bars: 16 & 20 = 250 !lm; 17 & 19 = 100 !lm; 18 = 25 !lm.

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Fibres non-septate, diameter 18-24 11m, walls c. 4 11m thick, occasionally gelatinous, small simple pits rather numerous in radial walls; length 850 (700-950) 11m. F IV ratio: 1.37. Rays uniseriate; 16 per mm. Two types present, one type composed exclusively of upright cells, the other type an irregular mixture of procumbent, square and upright cells, though usually with many marginal rows of upright cells; vertically compound rays also present. Height very variable, up to 1 mm or more; width 8-14 11m. Rhombic crystals present, often in chambered cells. Parenchyma apotracheal, diffuse and in one-cell-wide, often interrupted bands, dif­ ficult to distinguish from fibres as both have cells of equal diameter. Strands of 4(-8) cells.

Note: The collection Maguire 42212 and an additional wood sampie were originally distributed as Sapium yutajense Jablonski. In Kruijt's thesis (1989: p. 201) the speci­ men, mainly based on wood anatomical characters, was transferred to Senefelderopsis yutajense (labl.) Mennega. Finally Esser (1993) considered that the plant did not fit in any of the existing genera of the Mabeinae and he consequently created a new genus Dendrothrix, closely related to Senefelderopsis and less closely to Senefeldera.

Excoecaria L. - Fig. 17, 18 A genus of 20-30 species, occurring in tropical and subtropical Asia and Africa.

Material studied: E. agallocha L.: India: For. Inst. Dehra Dun (Tw 22536); Philippines, Quezon: FPRI 223.

General features: A soft, light brown to cream coloured wood without distinction between heart- and sapwood; texture straight, moderately fine; density c. 0.40.

Microscopic features: Growth rings present but faint, boundaries forrned by a narrow zone of radially compressed fibres. Vessels diffuse, 30-40% solitary, remainder in radial multiples of 2-4(-6), few in clusters or twin-multiples; 13 (7-20) per sq. mm. Outline circular or slightly angular, diameter 80-100 11m; vessel element length 675 (450-900) 11m. Perforations simple, intervessel pits alternate, circular, 5-8 11m wide, vessel-ray pits similar to intervessel pits, borders not reduced. Thin-walled tyloses occasionally present. Fibres non-septate, very thin-walled, diameter 20-24 11m, walls 2-3 11m thick, part of the fibres with gelatinous walls; pits minutely bordered, mainly in radial walls. Length 990 (600-1170) 11m. F/V ratio 1.47. Rays mostly uniseriate, but occasionally biseriate or locally 2 cells wide; 9-11 per mrn. Composed of rather high procumbent cells and large square cells, upright cells scarce. Height variable, usually 8-15 cells (c. 400 11m) but also up to 30 cells (over 1000 11m) high; width 20-25 11m. Intercellular spaces conspicuous. Laticifers present in several rays. Rhombic crystals frequent in all types of cells. Parenchyma apotracheal in rather numerous, one- to two-cell-wide, slightly wavy bands, 6-8 per mm. Strands of 2-4 cells.

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Note: The generic description had to be based on a single species. Wood samples of other species labelled Excoecaria were available as well as descriptions, but consider­ able differences in wood features cast doubt on the identifications. Janssonius (in Moll & Janssonius 1934) described the wood ofthe Javanese species E. agallocha, E. macrophylla, and E. virgata. Though he considered the three wood samples as closely related, evidence from the present study justifies exclusion of E. macrophylla and E. virgata from Excoecaria. The latter species was transferred by Esser (1999b) to Shirakiopsis virgata (Merr.) Esser; this is in accordance with the anatomi­ cal features as described by Janssonius. Excoecaria macrophylla 1.1. Smith (1910) is a synonym of E. bantamensis Muell. Arg. (cf. Govaerts et al. 2000). The wood differs by its reddish brown colour, the presence of crystals in chambered parenchyma cells and by rather numerous, narrow vessels. Wood blocks of E. myrioneura Airy Shaw (1980) from Irian Jaya (Lw: BW 2421, 2780,9729, 10507) did not match wood of E. agallocha either, e.g. by the abundance of silica in ray cells, and by the large, irregular, gash-like vessel-ray pits. According to Esser et al. (1997) the species, only known from non-flowering or fruiting collec­ tions, certainly does not belong to Excoecaria, but it proved impossible to identify the sterile herbarium material. He even considered its position in Hippomaneae doubtful. The wood anatomy supports its exclusion from Excoecaria. Govaerts et al. (2000: p. 1608) treat the species as of uncertain position, but possibly belonging to Euphor­ bieae, which is not contradicted by its wood anatomy. The commercial wood "tambootie" from southem Africa is either cited as E. ajricana (Sond.) Muell. Arg. (Kribs 1968; Kromhout 1976) or as Spirostachys ajricana Sond. Another African species, E. venenifera Pax, has also been transferred to Spirostachys. As discussed under Spirostachys, Norrnand and Detienne (1992), following their wood anatomical study, are strongly in favour of considering Spirostachys a syno­ nym of Excoecaria. Esser (1994,2001) too considers Excoecaria and Spirostachys as closely related, but nevertheless keeps them apart. In the present study it is treated as Spirostachys. Another suggestion was offered by Esser et al. (1997), i. e. to unite Excoecaria and Sebastiania. This has, however, not yet been realised because the genus Sebastiania is in need of revision. Wood anatomy supports this suggestion.

Falconeria Royle - Fig. 19,20 A monotypic genus, occurring in South and East Asia.

Material studied: F. insignis Royle: India: Birla Institute (Tw 45179).

Generalfeatures: Small to large tree. Wood spongy, soft, light creamy yellow; straight­ grained.

Microscopic features: Growth rings mostly inconspicuous, boundaries indicated by a few rows of radially compressed fibres, occasionally with gelatinous walls, also by wider vessels at the beginning of a new ring.

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Vessels diffuse, about 25% solitary, remainder in radial multiples of 2-3, or in lon­ ger, often double chains dumbbell-shaped; 5 (1-7) per sq. mm. Outline oval, diameter variable, 80-200 I!m, vessel element length 710 (600-900) I!m. Perforations simple, intervessel pits alternate, polygonal, 8-10 I!m; vessel-ray pits large, irregular, roundish to elongate, with strongly reduced borders. Fibres non-septate, diameter c. 24 I!m, walls thin, occasionally gelatinous, pits nu­ merous, with minute border, restricted to radial walls. Length 1070 (830-1290) I!m. FIV ratio 1.51. Rays uniseriate, with conspicuous intercellular spaces; 12 per ffiffi. Composed of pro­ cumbent, square and upright cells; procumbent cells generally relatively short and rather high, grading into square cells. Height strongly variable, 300-1000 I!m (2-25 cells); width 20-30 I!m. No contents. Narrow laticifers occasionally present. Parenchyma apotracheal in rather regularly spaced, one-cell-wide, often interrupted bands; c. 9 per mm. Strands of 4-8 cells. Rhombic crystals numerous in chambered cells.

Note: The taxon used to be incorporated in Sapium and the wood sampie was distributed accordingly as S. insigne. The wood structure closely resembles that of Sapium, differing mainly by the presence of crystals in the parenchyma instead of in the ray tissue.

Grimmeodendron Urb. A genus of 2 species restricted to Jamaica, Cuba and the Bahamas.

Material: Not available, see Note.

Microscopic features: Growth rings vague. Vessels diffuse, solitary and in radial multiples as weIl as often in clusters; 14 per sq. mm. Perforations simple, walls 4-5 I!m thick, intervessel pits alternate, polygonal, about 10 I!m; element length 272-800 I!m. Fibres 14 I!m in diameter, walls 5 I!m, length 624-1280 I!m. Rays uniseriate; 10 per mm. Composed exclusively of procumbent cells. Width 14 I!m. Parenchyma unilateral vasicentric and apotracheal in tangential bands of c. 6 cells. Strands of 4-9 cells. Rhombic crystals present in chambered cells.

Note: The data presented above are taken from a description in 'Cuban Woods I' by Carreras and Vales (1986). The wood differs from most genera of the tribe by its ho­ mocellular rays, an unusual feature also present in Hippomane and Pleradenophora.

Gymnanthes Sw. - Fig. 21-25; Table 3 A mainly subtropical and tropical South American genus with few species in tropical Africa and Asia. Number of species as suggested by Esser (2001) and Webster (1994) 40-45, though the exact number is strongly dependent on the botanist's species concept in this still insufficiently studied complex (see Note).

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Fig. 21-25. Tribe Hippomaneae: Gymnanthes. - 21 & 22. G. borneensis, Og-B 160. -21: Trans­ verse section showing variation in vessel arrangement. - 22: Tangential seetion; rays uni- and biseriate. - 23. G. lucida, A.F. Wilson F 41. Transverse seetion showing narrow vessels, and rhombic crystals in uniseriate rays. - 24. G. hypoleuca var. intermedia, Krukoff7269. Tangen­ tial section showing very small intervessel pits. - 25. G. schottiana, Hatschbach & Lindeman 13937. Radial seetion, with small silica grains. - Scale bars: 21 = 250 I-tm ; 22-24 = 100 I-tm; 25 = 40 I-tm .

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Table 3. Selected characters in Gymnanthes.

Species Vessels Contents of ray cells number width in !Am pits silica crystals

G. borneensis 6-17 100-130 7-9 large absent G. hypoleuca 13-28 60-70 9-12 G. klotzschiana 20-50 40-80 9-12 large present G.lucida 40-60 25-40 8-11 large present G. schottiana 25-46 30-60 8-10 small absent

Material studied: G. borneensis (Pax & K. Hoffrn.) Esser: Malaysia: (Og-B 160) - G. hypoleuca Benth. var. intermedia Muel!. Arg.: Brazil: Krukoff7269 - G. klotzschiana (Muell. Arg.) Muell. Arg. var. klotzschiana: Brazil, Parana: Lindeman & H. de Haas 203, 686,1002,1288,1571, 1648,2039,2284,3005,3397,3420,3428,3469; Brazil: (Bw s.n.) - G. klotzschiana var. trichoneura Muel!. Arg.: Brazil, Parana: Lindeman & H. de Haas 1220 - G.lucida (Sw.) Rothm.: USA, Florida: A.F. Wilson F 41, Florida Keys: Stern & Brizieky 413, 541 (MAD-SJRw 51211 resp. 51317), Stern 1452 (USw 25377); Guadeloupe: Rollet 1122 (CTFf 28489); Portorieo: A. Stahl 6 (Bw s.n.) - G. schot­ tiana (Muel!.Arg.) Muel!.Arg.: Brazil, Parana: Hatsehbaeh & Lindeman 13937.

General features: Siender trees, 5-10 m tall. Wood straw-eoloured, usually without distinetion between heart- and sapwood, but in G. lucida with dark brown heartwood. Hard, fine-textured, straight-grained; density 0.52-0.77, in G.lucida 1.10.

Microscopic features: Growth rings generally absent or vague, if present indieated by a narrow boundary zone of radially eompressed fibres. Vessels 10-20% solitary in G. borneensis and G. klotzschiana, 30-40% solitary in the other speeies, remainder in radial multiples of 2-6(-8), in twin rows and clusters; diffuse, though in G. hypoleuca and G. klotzschiana with indieation of radial arrange­ ment; 12-40 per sq. mm, in G. lucida 50-100. Outline elliptie, diameter in most spe­ eies 40-80 flm, in G.lucida 25-40 flm, in G. borneensis 100-140 flm, vessel element length 550 (480-630) flm. Perforations simple, intervessel pits with a wide range: in G. hypoleuca 5-6 flm wide, in G. borneensis and G. klotzschiana 10-12 flm wide, in the other speeies 8-10 flm wide, polygonal, apertures often coaleseent in G. hypoleuca; vessel-ray pits erowded, half-bordered, of the same size as the intervessel pits, in G. borneensis larger, elongate pits with strongly redueed borders oeeasionally present. Fibres non-septate, diameter 15-20 flm, walls 2-4 flm thiek, in G. lucida 5-6 flm thiek, often gelatinous in all speeies. Pits minute, almost restricted to radial walls. Length 870 (836-900) flm, in G. borneensis 1245 (1050-1500) flm. F/V ratio: l.60 (1.48- 1.76). Rays exciusively uniseriate in G. lucida, in the other species mainly uniseriate, but occasionally biseriate; 20-22 per mm. Heterogeneous, composed of procumbent, square and upright cells in irregular arrangement in G. lucida, but more regular in the other species with a central part of procumbent cells and the other cell types in the

Downloaded from Brill.com10/09/2021 12:24:23AM via free access 24 IAWA Journal, Vol. 26 0), 2005 high ray margins; vertically fused rays in G. klotzschiana and G. lucida. Cell walls often strongly disjunctive. Perforated ray cells present. Width in G. lucida 16-20 !lm, in the other taxa 22-32 !lm; height very variable, in G. lucida usually not over 700 !lm high, in the other species from 200-1400 !lm, occasionally up to 2000 !lm. Contents not noticed in G. hypoleuca, numerous rhombic crystals and also large silica bodies in G. klotzschiana and G. lucida I), exclusively large silica bodies in G. borneensis and small silica bodies in G. schottiana. Parenchyma apotracheal, in one-, occasionally two-cell-wide, wavy, often interrupted bands, c. 9 per mm. Strands of 4-8 cells. No contents.

Note: In this genus the species are rather variable in their anatomy reflecting partly the taxonomists' difficulties in defining the genus (Esser et al. 1997). In particular the discrepancy in ray cell contents is unusual as compared to the uniformity of contents in the other genera of the subfamily. In a cladogram of Malesian Hippomaneae (Esser et al. 1997) Gymnanthes is in a clade with Shirakia (later Neoshirakia japonica) and Shirakiopsis species, a relationship partly reflected in the wood anatomy. Actinostemon, often considered as closely related, or even as a synonym by Webster (1994), is characterized by the simultaneous presence of striking vesselless radial zones, small intervessel pits and large silica bodies in ray cells. In Gymnanthes p.p., the following features should be noted: in G. hypoleuca and G. klotzschiana a tendency to a similar unequal vessel distribution is present; the large silica inclusions in the ray cells of G. klotzschiana and G. lucida almost match those of Actinostemon. Intervessel pits are small in G. hypoleuca, as in Actinostemon.

Hippomane L. - Fig. 26, 27 A genus of 5 species occurring in Mexico and the West Indies.

Material studied: H. mancinella L.: Guadeloupe: Karsten 495 (Bw); USA, Summerland Key: Stern & Brizicky 351 (MAD-SJRw 51168).

General features: Tree with lustrous yellowish brown heartwood, with markings of brown and black, sapwood yellowish; texture fine; density 0.60-0.68 (data taken from Record & Hess 1943).

Microscopic features: Growth rings absent. Vessels diffuse, 60-70% solitary, remainder in radial multiples of 2 or 3, in clusters and in dumbbell-shaped multiples; 11 (8-24) per sq. mm; outline round to oval, diameter 70-140 !lm, vessel element length 565 (400-780) !lm. Perforations simple, interves­ seI pits 10 !lm, alternate, polygonal, apertures occasionally coalescent; vessel-ray pits large, horizontally or obliquely scalariform or similar to intervessel pits, with slightly to strongly reduced borders. Tyloses occasionally present. Fibres non-septate, diameter 16-20 !lm, thin-walled, walls c. 2 !lm thick, partly gelatinous; pits smalI, bordered, restricted to radial walls. Length 900 (667-1150) !lm. F/V ratio 1.60.

I) Also present in twig wood of G. longipes (Croat 3954, identified by M. J. Huft).

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Fig. 26-29. Tribe Hippomaneae. - 26 & 27. Hippomane mancinella, Stern & Brizicky 351. - 26: Transverse seetion. - 27: Tangential seetion showing rather short, almost homocellular uniseriate rays. - 28 & 29. Mabea, radial seetions. - 28: M. taquari, Breteler 3834, liana. Rays with numerous large silica bodies. - 29: M. piriri, Stahel 212. Ray with three narrow laticifers (arrowheads), silica lacking. - Scale bars: 26,27 & 29 = 100 flm; 28 = 25 flm.

Rays exclusively uniseriate, 12 per mm, composed of procumbent and square cells, procumbent cells not sharply delimitated from square cells, often the marginal rows composed of square cells. Height up to 400 11m (6-16 cells), width 16-20 11m. Rhombic crystals frequently present in all cell types, either large and solitary or small and several in a cello Laticifers rare, noticed only in one sampIe.

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Parenchyma apotracheal in one- (or two-)cell-wide bands, the bands often interrupted, tangential or somewhat oblique. Strands of 4-8 cells; occasionally cells chambered by a thin septum. Crystals frequent.

Note: Hippomane differs in its anatomy from the other genera of the tribe by the low, almost homocellular rays and the narrow fibres in particular. An identical type of rays occurs in Grimmeodendron and Pleradenophora.

Mabea Aublet - Fig. 28, 29 A large genus of about 50 species, restricted to Central and South America.

Material studied: M. angularis Hollander: Brazil, Rio Madeira: Krukoff 1502 (type), 8785 - M. klugii Steyerm.: Brazil: Krukoff 7168 - M. montana Muell. Arg.: Panama: Stern et al. 1930 (USw 33725); Venezuela: LI. Will. 10214; Guyana: Jansen-Jacobs et al. 4585 - M. nitida Spruce ex Benth.: Brazil: Krukoff 6400, Prance et al. 14031; Peru: Maas et al. 6239 - M. occidentalis Benth.: Venezuela: de Bruyn 1230, Maas et al. 5100 - M. paniculata Spruce & Benth.: Brazil: Krukoff 1317 - M. piriri Aubl.: Suriname: Stahe1212, Lanjouw & Lindeman 2438, Lindeman 4581, Heyde & Lindeman 159, LBB (Maas) 10773, van Donselaar 3763; Guyana: For. Dept. 3419, Jansen-Jacobs et al. 333, Maas et al. 7504; Venezuela: Breteler 3796,5014; Peru: Maas et al. 6291; Brazil: Krukoff 6154 - M. pulcherrima Muell. Arg.: Guyana: Jansen-Jacobs et al. 1498; Suriname: Lindeman etal. 919; Brazil: Krukoff8210 - M. speciosa Muell. Arg. subsp. guianensis Esser: Suriname: Daniels & Jonker 1161, Maguire et al. 24886 (Yale 44285) - M. speciosa subsp. obovata (Muell. Arg.) Esser: Guyana: Maas et al. 5913; French Guiana: de Granville et al. 6417 - M. speciosa subsp. speciosa: Suriname: Lanjouw & Lindeman 2432, 2879; Brazil: Krukoff 6681,6918 - M. taquari Aubl.: Suriname: Lanjouw & Lindeman 1193, Mennega 354; Venezuela: Breteler 3834; Brazil: INPA 6237; Guyana: Maas et al. 7255.

General features: Trees, shrubs, occasionally lianas with a light coloured yellowish brown wood, straight-grained, moderately fine-textured; density 0.68-0.83. Narrow to wide lysigenous radial cavities often present.

Microscopic features: Growth rings obscure or clearly visible, indicated by a narrow boundary of thick-walled, flattened fibres and absence of parenchyma. Vessels diffuse, 20-50% solitary, remainder in radial multiples of 2-3(-6) and in clusters; on average 5-15 per sq. mm, in the liana M. taquari 23 (18-27) per sq. mm. Outline round to oval, diameter variable, mostly 100-140 !lm, but 40-80 !lm in M. speciosa var. concolor and in M. klugii, up to 280 !lm in the liana M. pulcherrima. Vessel elements often with long pointed ligulas, length on average 730 (600-830) !lm. Perforations simple, intervessel pits 8-10(-12) !lm, border roundish or elongate and angular; vessel-ray pits large, 12-18 !lm, elongate or irregular, with moderately to strongly reduced borders. Thin-walled tyloses present in most species. Fibres non-septate, walls moderately thick, c. 4 !lm, occasionally gelatinous and occluding the lumen, diameter 16-20(-24) !lm. Pits smalI, restricted to radial walls. Length 1190 (900-1380) !lm. F/V ratio 1.5-1.8.

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Rays uniseriate (exceptionally 2 cells wide over a short range); 15-20 per mm. Heterocellular, the cell types irregularly distributed, procumbent cells relatively high and short. Sometimes two types of rays present, one exclusively composed of upright cells, the other type with various cell types, often vertically fused. Width 15-20 flm; height up to 2500 flm, generally from 600-1000 flm. Laticifers noticed in M. angularis, M. nitida, M. occidentalis, M. piriri, M. pulcherrima, and M. speciosa subsp. speciosa. Silica bodies present in procumbent and square ray cells of all species investigated, rather large in M. montana and M. piriri. In M. occidentalis occasionally rhombic crystals, as weIl as bars of Sanio. Parenchyma apotracheal in numerous two- to three-cell-wide, wavy, often interrupted bands and as isolated strands, in M. occidentalis the short bands one cell wide; number of bands ranging from 5 to 12 per mm. Strands of 4-8 cells. Crystals often noticed in M.occidentalis.

Note: The wood of the genus is very uniform. Remarkable is the simultaneous occur­ rence of silica and crystals in M. occidentalis. This characteristic was also noticed in Gymnanthes klotzschiana and Senejelderopsis croizatii, taxa also closely similar in other respects.

Maprounea AubI. - Fig. 30-33 A genus of 5 species occurring in tropical America and Africa.

Material studied: M. africana MuelI. Arg.: E. Africa: Schlieben 353, 1761 (RBw); Angola: Dechamps et al. 1482 - M. brasiliensis A. St. HiI.: Brazil: Maguire 57141 - M. guianensis AubI.: Suriname: Stahel27, BBS 143, LBB 10729, Lindeman 5286, 5753, Schulz 7365; Guyana: F. D. 3330; Brazil, Amapa: Belem 51745 (= Maguire); Amazonia, Krukoff 6678,7067; Colombia: For. Dept. s.n. - M. spec.: Brazil: Maguire 56473.

Generalfeatures: Medium-sized trees with light coloured, yellowish brown or crearnish yellow wood without differentiation in sap- and heartwood; straight-grained, texture fine; density 0.65-0.75.

Microscopic features: Growth rings present, indicated by narrow boundaries of radi­ ally compressed fibres. Vessels diffuse, rarely solitary, for 80-90% in radial multiples of 2-4(-8) and in clusters; 44 per sq.mm in M. africana, 11-16 per sq.mm in the American species; outline oval, diameter (60-) 130(-150) flm, vessel element length 656 (510-900) flm. Perforations usually simple but occasionally a scalariform perforation with few to several bars present; intervessel pits small, diameter 5-7 flm, the apertures often coa­ lescent; vessel-ray pits oftwo types, generally small in procumbent cells and large and irregular, with strongly reduced borders in square cells, though both types mayaiso occur in the same cello Thin-walled tyloses occasionally present. Fibres non-septate, walls 4-5 flm thick, often gelatinous in M. guianensis, diameter about 20 flm in M. africana and in M. brasiliensis, up to 30 flm wide in M. guianensis; pits very numerous in radial walls, C. 2.5 flm wide with a small border; intrusive cavi­ ties present; length 995 (780-1275) flm. F/V ratio 1.53.

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Fig. 30-33. Tribe Hippomaneae. Maprounea. - 30-32. M. guianensis. - 30: Stahel27. Trans­ verse seetion. - 31: Krokoff 6678. Radial seetion showing different sizes of vessel-ray pits. - 32: Krukoff 7067. Maceration; two vessel elements and a lO-celled parenchyma strand. - 33. M. africana, Schlieben 353. Maceration showing a fibre with an intrusive cavity. - Scale bars: 30 = 250 !im; 31 & 33 = 40 !im; 32 = 100 !im.

Rays uniseriate and biseriate; 14-17 per rnrn. Uniseriates cornposed of procurnbent and square cells, upright cells very few; biseriates in varying nurnbers, up to 50%, rnost­ ly with a short, 2 cells wide central part, and with uniseriate wings of variable height, often asyrnetrical; vertically fused rays nurnerous. Width 16-20 flrn; 50-1000 flrn (2-32

Downloaded from Brill.com10/09/2021 12:24:23AM via free access Mennega - Wood anatomy oi the Euphorbioideae (Euphorbiaceae) 29 cells) high. Crystals rare, though noticed in ray cells of all species. In M. brasiliensis crystals as well as silica bodies present; in M. guianensis the presence of small silica bodies, as reported by Espinoza de Pemfa (1987) for this species, is confirmed. Parenchyma apotracheal, in one- to two-cell-wide bands, and diffuse; bands wavy, often interrupted, 7-12 per mm. Strands of 4-8(-12) cells.

Note: Maprounea is exceptional by the occasional occurrence of scalariform vessel perforations, a feature more often present in the other subfamilies. According to Esser (pers. comm.), Maprounea is an isolated genus, without close relationships. Perhaps it should be considered as a basal taxon within the tribe.

Neoshirakia Esser - Fig. 34, 35 A monotypic genus in Japan and East Asia, established in 1998 by Esser, who also coined the name Neoshirakia for the genus known before as Shirakia Hurus.

Material studied: N. japonica (Siebold & Zucc.) Esser: Japan (Coi. For. Exp. Station 2252, Tw 17637); S. Korea: For. Res. lust. Seoul (Tw 42390, Lw s.n.).

Generaljeatures: Trees with straw-coloured wood. Sampies too small for additional information.

Microscopicjeatures: Growth rings inconspicuous, though boundaries sharply indicated by one row of compressed fibres. Vessels diffuse, 50-60% solitary, remainder in radial multiples of 2-5, in clusters and twin rows; 22 (15-28) per sq. mm. Outline more or less circular, thick-walled, diameter 30-70 !-lm, length ofvessel elements 621 (470-800) !-lm. Perforations simple, intervessel pits 7-10 !-lm, apertures occasionally coalescent; vessel-ray pits identical or slightly smaller. Fibres non-septate, diameter 15-20 !-lm, walls c. 4!-lm thick, gelatinous layer almost always present; pits minute, simple or with a narrow border, restricted to radial walls. Length 1050 (920-1280) !-lm. F/V ratio 1.67. Rays uniseriate, 14 per mm. Composed mainly of square or an intermediate type of cells, but also truly procumbent and upright cells present, often intermingled. Width c. 14 !-lm, height usually 250-500!-lm (5-12 cells), seldom up to 1000 !-lm. No contents noticed. Parenchyma apotracheal, in one-cell-wide, often interrupted, straight or undulating bands; about 7-9 per mm. Strands of 4-8 cells. Rhombic crystals in chambered cells occasionally present.

Note: Neoshirakia japonica Esser (Esser 1998), a taxon originally placed in Stillingia, next in Excoecaria and finally by Pax and K. Hoffmann in Sapium, was transferred by Hurusawa (1954) to Shirakia. Kruijt (1989) expanded Shirakia by incorporating three Old World species of Sapium: S. aubrevillei, S. elliptica, S. virgata. The wood of these species contains silica in the ray cells, a substance never present in Sapium, and therefore the anatomy supports the transfer in this respect. On the other hand, silica is not present in another species of Shirakia: S. japonica; occasionally crystals were

Downloaded from Brill.com10/09/2021 12:24:23AM via free access 30 IAWA Journal, Vol. 26 (I), 2005 noticed in parenchyma cells but not in ray cells like in Sapium. Esser's concept of a new genus for Shirakia japonica is therefore supported by wood anatomy. The occurrence of crystals in chambered parenchyma cells was also observed in Fal­ coneria insignis, Pleradenophora and Triadica . ... 11:1 1 ~ 11 ~~

~~

~.~ 'f-" .... ~ jl ~';' , \1 l;jft~~~ ~: i t~~ ~t' I~ ' ~!. 11 '--

Fig. 34-37. Tribe Hippomaneae. - 34 & 35. Neoshirakiajaponica, Tw 42390. - 34: Transverse section. - 35: Radial section, showing perforated ray cel!. - 36. Pleradenophora longicuspis, MADw 23129. Tangential section; uniseriate rays of mainly procumbent cells. - 37. Pseudo­ senefeldera inclinata, Krukoff7126. Transverse section, showing radial strips without vessels. - Scale bars: 34 = 100 ~m; 35 = 35 ~m; 36 = 50 ~m; 37 = 160 ~m .

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Pleradenophora Esser - Fig. 36 A genus of at least 4 species in Guatemala, Honduras, Mexico, and probably the USA.

Material studied: P. longicuspis (Standl.) Esser: Guatemala, Peten (MADw 23129).

Generalfeatures: Trees with straw-coloured, straight-grained wood, moderately hard; density 0.66.

Microscopic features: Growth rings present, indicated by boundaries of a few rows of radially compressed fibres, differentiating between a large zone of fibres with a ge­ latinous inner layer and a zone of wood fibres with slightly thicker walls and without gelatinous layers. Vessels diffuse, about 36% solitary, remainder in radial multiples of 2-4; 14 (12-18) per sq. mm. Outline oval, diameter c. 90 f!m; vessel element length 595 (420-860) f!m. Perforations simple, intervessel pits 8 f!m, the borders rectangular; vessel-ray pits cir­ cular, 6-8 f!m wide, crowded, half-bordered. Fibres non-septate, diameter about 25 f!m, walls c. 4 f!m, with a gelatinous inner layer in zones of earlywood. Pits minute, restricted to radial walls. Length 1020 (720-1250) f!m. F/V ratio 1.71. Rays uniseriate; 14 per ffiffi. Weakly heterocellular, mainly composed of procumbent cells, about 24 f!m high, and 60-100 f!m long, bordered by a row of square cells. Width 12-15 f!m, height about 400 f!m (18 cells). No contents. Parenchyma apotracheal, in one- to two-cell-wide, slightly undulating, often inter­ rupted, regularly spaced bands. Strands of 4-8 cells. Contents: rhombic crystals solitary, or more than one and then of different sizes in a cello

Note: The species originally known as Sebastiania longicuspis Standl. differs in its wood structure from S. brasiliensis, a true Sebastiania, by shorter rays chiefly composed of procumbent cells, by presence of crystals in the parenchyma, and absence of crystals in the rays. Relationship with Sapium and Stillingia as suggested by Esser (2001) is not reflected in wood anatomy as far as the crystal distribution and ray structure are concemed.

Pseudosenefeldera Esser - Fig. 37 A monotypic genus of the Amazon region of South America.

Material studied: P. inclinata (Muell. Arg.) Esser: Brazil: Krukoff7126, USw 8193.

Generalfeatures: Slender trees with a fine-textured, hard, yellowish wood. With a hand­ lens radial zonation is visible on cross section.

Microscopicfeatures: Growth rings conspicuous by boundaries ofnarrow, wavy bands of radially flattened fibres. Vessels about 10% solitary, remainder in radial multiples of2-8, sometimes in twin rows, and clusters; distribution in radial zones, altemating with zones without vessels;

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32 (22-41) per sq. mm. Outline oval, diameter 70 (50-100) !-lm; vessel element length 735 (600-865) !-lm. Perforations simple, intervessel pits alternate, polygonal, diameter 8-12 !-lm; vessel-ray pits irregular, generally large, oval, with strongly reduced borders. Moderately thick tyloses occasionally present. Fibres non-septate, diameter 17-20 !-lm, walls c. 4 !-lm thick; in regular rows; nu­ merous, very small, simple pits restricted to radial walls. Length 930 (830-1040) !-lm. F/V ratio 1.26. Rays generally uniseriate, some biseriate over a variable distance; 15-20 per mm. Composed of a central part of procumbent cells of variable dimensions, sometimes mix­ ed with square cells, margins short to rather long, of square and rather short (60 !-lm) upright cells, irregularly distributed, but also rays exclusively composed of square and upright cells, and vertically fused rays present. Cell walls thick, often disjunctive, particularly in the square and upright cells. Height variable, up to 2 mm; width 15-30 !-lm. Laticifers present but rare. Large silica bodies, filling the cell lumen present in numerous procumbent and square cells. Parenchyma apotracheal in short, one-cell-wide, rather regular wavy bands, the bands partly continuous, partly interrupted; 8-9 per mm. Strands of 4-8 cells.

Note: Esser (2001) established the genus Pseudosenefeldera with as only species P. in­ clinata (synonyms: Senefeldera inclinata, S. karsteniana, and S. nitida). The sampie Krukoff 7126 is the type of S. nitida. The striking radial vesselless zones as seen in cross section as weIl as the large silica inclusions in numerous ray cells occur also in Actinostemon, Rhodothyrsus and less pronounced in Gymnanthes p.p.

Rhodothyrsus Esser - Fig. 38-41 A neotropical genus of 2 species, one from the Amazonian rain forest, the other from NW. Venezuela.

Material studied: R. macrophyllus (Ducke) Esser: Brazil: Krukoff 6922; Guyana: Jansen-Jacobs et al. 2509; Colombia, Araracuara: MSS 1079.

Generalfeatures: Low trees or shrubs with yellowish brown, fine-textured, hard wood; density c. 0.90.

Microscopic features: Growth rings faint to rather evident, boundaries of a few rows of compressed fibres. Vessels about 60% solitary, remainder in radial multiples of 2-4 or even much longer chains, occasionally paired or dumbbell-shaped. Distribution in radial zones; 18-30 (10-39) per sq. mm. Outline round to elliptic, diameter 80 (60-90) !-lm; vessel element length 965 (710-1270) !-lm. Perforations simple. Intervessel pits 8-12 !-lm, with slightly angular borders. Vessel-ray pits partly round and of the same size as intervessel pits, partly larger, elongate or kidney-shaped, with slightly reduced borders. Fibres non-septate, diameter 16-20 !-lm, walls c. 3 !-lm thick, occasionally gelatinous. Pits in radial walls, very small, simple. Length 1170 (870-1370) !-lm. F IV ratio 1.22.

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11 ~! ,\' ~F ,I ~: tr!

) 0\ '11

t Ir . If ~ ,. ,:.'

Fig. 38- 41. Tribe Hippomaneae. Rhodothyrsus macrophyllus. - 38-40. Jansen-Jacobs et al. 2509. - 38: Transverse seetion, growth ring boundaries with radially compressed fibres (arrow­ heads). - 39: Tangential seetion, showing uniseriate rays. - 40: Radial seetion; procumbent cells rather short and high; silica inclusions in all cell types. - 41. Krukoff 6922. Radial SEM photo­ graph showing vessel-ray pits. - Scale bars: 38 & 39 = lOO 11m; 40 =40 11m; 41 =25 11m.

Rays uniseriate, seldom locally biseriate; 18 (16-20) per mm. Irregularly composed of rather short procumbent cells, square cells and upright cells, the latter c. 80 !-lm high; some rays composed exclusively of procumbent or upright cells. Width c. 15 !-lm; height

Downloaded from Brill.com10/09/2021 12:24:23AM via free access 34 IAWA Journal, Vol. 26 (I), 2005 very variable, from 4-40 cells (100-1400 !-lm), Large silica bodies occurring in all cell types, though mainly in the procumbent cells, Parenchyma apotracheal in wavy bands, mostly two cells wide, continuous or often interrupted, Strands of 6-8 cells,

Note: Esser (1999a) transferred the species Senefeldera macrophylla to the new genus Rhodothyrsus, The wood of this taxon shows the same characteristic features of radial vesselless zones and large silica bodies in the ray cells as Actinostemon and Pseudo­ senefeldera. Of the three species still remaining in Senefeldera, ranging from Panama to Brazil, no wood was available for comparison.

Sapium Jacq. - Fig. 42-44 A New World genus of 21 species.

Material studied: S. glandulosum (L.) Morong: Guadeloupe: CTFT 27765 (ONF Lo­ catin 7); Venezuela: Karsten 35, L. Williams 10 176, Steyermark 86543, Breteler 4027; Panama: (U.S. Nat. Herb. 679819); Guyana: Jansen-Jacobs etal. 4233; Suriname: BBS 142, Lanjouw & Lindeman 1381, Geyskes s.n., Stahel216; French Guiana: Kruijt 37; Ecuador: Acosta-Solis 5833; Brazil: Krukoff 6158, Froes 62, Lindeman & de Haas 3602, Maguire et al. 51948; Uruguay: Lebacq (Tw 20489) - S. haematospermum Muel!. Arg.: Brazil, Parana: Lindeman & de Haas 4830 - S.laurifolium (A. Rich.) Gris.: Cuba: Inst. Invest. For. 132 (Tw 47378); Peru: Ellenberg 2247, 2290: Colombia: Cua­ trecasas 15944, 16944; -So macrocarpum Muel!.Arg.: Costa Rica - S. marmieri Huber: Brazil: Krukoff 1656, 5717, 8098 - S. obovatum Klotzseh: Brazil: Krukoff 6296,6307 - S.pallidum (Muel!.Arg.) Huber: Brazil: Capucho 328 (Tw 27261)­ S. paucinervium Hemsl.: Guyana: For. Dept. 2703; Suriname: Lanjouw & Lindeman 2548, Lindeman 3552, 5950, 6187, 6451, 6801; French Guiana: Kruijt 17, Sabatier & Prevost 2151 - S. stylare Muel!. Arg.: Venezuela: Aristegueta 4235 (Tw 30447).

Generalfeatures: Shrubs or small trees, occasionally up to 20-30 m tall. Wood straight­ grained, rather coarse, soft to moderately hard, greyish beige-brown or tawny; density 0.30-0.70. Lysigenous cavities noticed in S. glandulosum and in S. marmieri.

Microscopicfeatures: Growth rings usually rather vague, boundary indicated by a num­ ber of rows of radially compressed fibres, in S. haematospermum by a zone of more numerous, smaller-sized vessels. Vessels diffuse, for the greater part in short radial multiples of 2-5 (65-90%), remainder in longer dumbbell-shaped chains, in twin multiples or in clusters; mostly 3-6 per sq. mm, more numerous (16-26 per sq. mm) in S. haematospermum. Outline usually oval, diameter mainly 60-200 !-lm, but occasionally up to 270 !-lm, vessel ele­ ment length 1060 (830-1350) !-lm. Perforations simple, intervessel pits alternate, oval to roundish, width (8-)10-12(-16) !-lm; vessel-ray pits large and numerous, variable, oval to kidney-shaped, sometimes in scalariform arrangement, with strongly reduced borders. Vascular tracheids present.

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Fig. 42-46. Tribe Hippomaneae. - 42-44. Sapium glandulosum, Karsten 35. - 42: Transverse section. - 43: Tangential seetion; uniseriate heterogeneous rays with tiny interceHular cavities (arrowhead) . - 44: Radial seetion showing variation in vessel-ray pits. - 45 & 46. Sclerocro­ ton. - 45: S. integerrimus, Schlieben 507. Radial seetion; vessel-ray pits with strongly reduced borders, some ceHs with large silica inclusions. - 46: S. schmitzii, Malaisse 10542. Tangential section showing intervessel pitting and heterogeneous rays, some ceHs with silica inclusions. - Scale bars: 42 = 250 !im; 43 & 44 = 100 !im; 45 & 46 =50 !im.

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Fibres non-septate with very small, bordered pits in the radial walls, walls thin, 2-4 flm thick, often part of the fibres with gelatinous walls, occasionally intrusive cavities present; diameter mostly 24-44 flm. Length 1668 (1360-2100) flm. F/V ratio 1.57 (1.36-1.81). Vascular tracheids present. Rays for the greater part uniseriate, occasionally biseriate over a short distance; 7-10 per mm. Heterocellular, the procumbent cells horizontally short and relatively high, in tangential sections resembling square cells, in some species truly procumbent cells present, in others upright cells scarce and restricted to marginal rows. Intercel­ lular spaces conspicuous (tangential section). Width 20-24 flm, rarely up to 30 flm, height mostly 400-900 flm, but up to 1800 flm. Large rhombic crystals often present in great quantities in all types of ray cells of most species, not noticed in S. marmieri, S. obovatum and S. pallidum. Latificers noticed in rays of S. obovatum, S. pallidum, S. paucinervium. Parenchyma apotracheal, in one- to two-cell-wide, partly fairly regular, partly wavy and interrupted bands; 6-10 per mm. Strands of 4-8 cells. Some vasicentric parenchyma noticed in S. marmieri, and occasionally in S. glandulosum. In one sampie of S. stylare a few crystals were noticed.

Note: In Kruijt's (1989,1996) critical generic revision several doubtfully related taxa were eliminated from Sapium, restricting the genus to the New World. The revised genus shows a great uniformity in wood structure, species mainly differing in size of vessel pits, width of fibres and presence of crystals. Laticifers were also observed in S. haematospermum by De Pompert (1989).

Sclerocroton Hochst. - Fig. 45, 46 The genus was re-established by Kruijt and Roebers (in Kruijt 1996). It is a taxon of about 6 species in tropical Africa and Madagascar.

Material studied: S. cornutus (Pax & K. Hoffm.) Kruijt & Roebers: W. Africa, Kasai: R. Dechamps 261 (Tw 10218) - S. integerrimus Hochst. (syn. Sapium armatum Pax & K. Hoffm.): E. Africa: Schlieben 507 (RBHw) - S. melanostictus (Baill.) Kruijt & Roebers: Madagascar: Dorr 2967, a twig sampie (Lw) - S. schmitzii (J. Leonard) Kruijt & Roebers: W. Africa, Zaire: Malaisse 10542 (Tw 38213).

Generalfeatures: Trees with hard, straight-grained, fine-textured wood.

Microscopic features: Growth rings present, not weIl defined, boundaries composed of a zone of radially compressed fibres. Vessels 15-35% solitary, the remainder in radial, often dumbbell-shaped or twin multiples; 14 (10-24) per sq.mm. Outline oval, diameter 70-120 (200) flm; length of vessel elements 550 (360-810) flm. Perforations simple, intervessel pits alternate, polygonal, 8-12 flm; vessel-ray pits of the same size, with strongly reduced borders, usually regularly distributed, though in S. schmitzii some large irregular pits sometimes occur.

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Fibres non-septate, diameter 16-20(-24) f..tm, walls 4-6 f..tm, often gelatinous, pits minute, bordered, restricted to radial walls. Length 970 (830-1200) f..tm. F/V ratio 1.74 ( 1.65-1.80). Rays exclusively uniseriate, occasionally 2-3 cells wide; 15-20 per mm. Heterocel­ lular, procumbent cells as high as square cells, upright cells rather low (60-80 f..tm). Width c. 18 f..tm, height mostly from 300 to 700 f..tm, some vertically fused and up to 1600 f..tm high. Large silica bodies abundant in all types of ray cells in all species. Parenchyma apotracheal, in numerous 1-2(-3)-cell-wide wavy and often interrupted bands. Strands of 4-8 cells. Rhombic crystals occasionally present.

Note: Pax and Hoffmann (1931) considered this taxon as a subgenus of Sapium. Wood anatomy supports the establishment of a separate genus, especially by the presence of silica bodies in ray cells, a feature never present in wood of Sapium. It is more diffi­ cult to find anatomical differences with Shirakia (now Shirakiopsis) species, in Pax 's opinion also bel on ging to Sclerocroton.

Sebastiania Spreng. - Fig. 51, 52 A New World genus of about 25 species distributed from Mexico to South Brazil.

Material studied: S. argutidens Pax et K. Hoffrn.: Brazil: Reitz & Klein 3841 - S. bra­ siliensis Spreng.: Brazil: Lindeman & H. de Haas 1381, 1830, 1846,2034,2209,3736, 4846.

Generalfeatures: Small to moderately tall, slender trees with white latex. Wood cream­ ish, no differentiation in heart- and sapwood, texture fine; density c. 0.70.

Microscopic features: Growth rings indicated by narrow boundaries of compressed fibres without gelatinous walls, sometimes also by absence of gelatinous fibres in the early wood. Vessels about 25% solitary, remainder in radial multiples of 2-6(-8), also often in twin rows, diffuse though with a tendency for radial arrangement; 40-60 per sq. mm. Outline mostly oval, diameter 40-80 f..tm; vessel element length 490 (340-560) f..tm. Intervessel pits alternate, with round borders, diameter 8-10 f..tm in S. argutidens, 12- 14 f..tm in S. brasiliensis; vessel-ray pits similar or slightly smaller, with slightly re­ duced borders. Fibres non-septate, walls often gelatinous, otherwise about 4 f..tm thick, diameter 16-20 f..tm, intrusive cavities occasionally present. Pits minutely bordered, mostly in radial walls but occasionally also a few in tangential walls. Length 880 (310-1270) f..tm. F/V ratio 1.46. Rays uniseriate, occasionally locally 2 cells wide; 17 per mm. Heterocellular with square, upright and some procumbent cells mixed, or exc1usively composed of upright and/or square cells; fused rays also present. Height variable, up to 1 mm (16 cells); width c. 16 f..tm. Contents: numerous large rhombic crystals, two or more in chamber­ ed cells in S. argutidens, solitary in S. brasiliensis. Intercellular spaces inconspicuous.

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Fig. 47-50. Tribe Hippomaneae: Senejelderopsis croizatii, Maas et al. 5828. -47: Transverse sec­ tion, most fibres with gelatinous walls. - 48: Tangential section. - 49: Radial section showing cells with silica globules and cells with crystals. - 50: Maceration; vessel member showing intervessel and vessel-ray pits. - Scale bars: 47 = 200 !Am; 48 = 100 !Am; 49 = 25 !Am; 50 = 50 !Am.

Parenchyma apotracheal in short, irregular, undulating, one- to two- cell-wide bands, occasionally in fairly straight bands, c. 7 per mm. Strands of 3-6(-8) cells. No contents.

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Note: Esser's (1994, 1999b) transfer of several New World species of Sebastiania (S. guyanensis (Muell. Arg.) Muell. Arg., S. klotzschiana (Muell. Arg.) Muell. Arg., S. schottiana (Muell. Arg.) Muell. Arg.) and two Malaysian species (S. borneensis Pax & K. Hoffm. and S. remota Steenis) to Gymnanthes left only two species ofthe former genus to be investigated, both showing a great structural sirnilarity. Relationship with Excoecaria was discussed under that genus. Available material of both genera is too scarce for asound conelusion. Though no striking differences were noticed, a elose relationship does not seem obvious either. The species eliminated and now accommo­ dated in Gymnanthes differ e.g. by the presence of silica in ray cells. The wood oftheArgentine taxon Dactylostemon (Actinostemon) anisandrus Griseb., described by Burgerstein (1912), and transferred to Sebastiania by Jablonski (1969), matches very weIl that of Sebastiania, e.g. by the presence of large crystals in ray cells.

Senefelderopsis Steyerm. - Fig. 47-50 A genus of two species restricted to the northern Neotropics.

Material studied: S. chiribiquetensis (R. Schultes & Croizat) Steyerm.: Colombia: Schultes 5484, 5535, 5623 - S. croizatii Steyerm.: Guyana: Maas et al. 5828.

Generalfeatures: Shrubs or trees, wood uniformly greyish brown with a purplish hue, fine textured, hard; density 0.73 (based on the stern specimen of S. croizatii).

Microseopie features: Growth rings vague, irregular, boundaries composed of a number of rows of compressed fibres. Vessels about 20% solitary, remainder in radial multiples of 2-4(-8), distribution dif­ fuse but with a tendency toward arrangement in radial zones; 11 (6-14) per sq. mm in S. croizatii, in twig material of S. chiribiquetensis 50-100 per sq. mm. Outline circular or slightly angular, diameter 80-150 f.tm, length ofvessel elements 580 (430-750) f.tm. Per­ forations simple, intervessel pits alternate, polygonal, 8-10 f.tm, wide apertures; vessel­ ray pits crowded, of the same size or slightly smaller than the intervessel pits; partly larger, of irregular form and with strongly reduced borders. Fibres mainly non-septate, diameter 18-20 f.tm, walls thin, occasionally gelatinous, intrusive cavities noticed. Small simple pits restricted to radial walls. Length 750 (600- 950) f.tm. FIV ratio 1.30. Rays uniseriate, exceptionally with a very short biseriate part; 14 (12-15) per mm. Mainly composed of a cell type intermediate between square and procumbent, mingled with rows of truly square cells, bordered either by square cells or by short upright cells. Width 20 f.lm, height mostly about 350 f.lm, but up to 800 f.tm. Laticifers only noticed in S. chiribiquetensis. Small (10 f.lm) silica bodies frequently present. Parenchyma mainly in one-cell-wide, often interrupted wavy bands, also some diffuse strands present. Strands of 4-8 cells. Rhombic crystals often present in non-chambered or chambered parenchyma cells.

Note: The combination of silica bodies in ray cells and rhombic crystals in parenchyma cells was also noticed in Sclerocroton.

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Fig. 51-54. Tribe Hippomaneae. - 51 & 52. Sebastiania brasiliensis, Lindeman & H. de Haas 2034. - 51: Transverse section; parenchyma bands difficult to recognize. - 52: Tangential section showing two types of uniseriate rays. - 53 & 54. Shirakiopsis elliptica, Dechamps 1534. - 53: Transverse section. - 54: Tangential seetion showing laticifers (arrowheads). - Scale bars: 51-54 = 100 fAm.

Shirakiopsis Esser - Fig. 53, 54 A genus of 6 species occurring in tropical Africa and Asia.

Material studied: S. aubrevillei (Leandri) Esser: Ivory Coast: Detienne 170 (Tw 29985) - S. elliptica (Hochst.) Esser: Angola: Dechamps 1534 (Tw 28170); E. Africa: Schlie-

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Generalfeatures: Trees up to 40 m high. Wood light yellowish brown, rather coarsely textured, soft and light. In S. virgata with brown, hard heartwood; density c. 0.65.

Microscopicfeatures: Growth rings present in S. elliptica and S. virgata, indicated by a boundary of severallayers of fibres with a narrow compressed lumen. Vessels diffuse, 30-50% solitary, the remainder in radial multiples of2-4, in S. vir­ gata frequently in longer multiples, or in twin rows; 1-5 (0-9) per sq. mm. Outline oval, diameter generally 150-220 f.lm; length of vessel elements 657 (340-1030) f.lm. Perforations simple, intervessel pits polygonal, large, 10-15 f.lm; vessel-ray pits crowded, rounded, with slightly reduced borders. Thin-walled tyloses notieed in S. vir­ gata. Fibres non-septate, diameter 25-40 f.lm, in S. virgata 20-24 f.lm, walls thin, about 3 f.lm. Most fibres with gelatinous walls. Pits minute, restricted to radial walls. Length 1100 (800-1500) f.lm. F/V ratio 1.68 (1.58-1.77). Rays uniseriate, sometimes locally biseriate in S. elliptica; 10-14 per mm. Irregu­ larly composed of mostly square and upright cells and of short and relatively high pro­ cumbent cells, but in S. virgata also truly procumbent cells, twice as long as high fre­ quently present. Width 20-25 f.lm; height usually not over 700 f.lm (15 cells), slightly higher in S. virgata. Laticifers c. 300 f.lm wide, noticed in S. indica, less large ones present in S. elliptica. In all species large silica bodies occurring in numerous square and procumbent cells. Parenchyma apotracheal in often interrupted, one- to two-cell-wide, slightly undulat­ ing bands, about 6-8 per mm. Strands of 4-8 cells. Rhombic crystals and crystal sand infrequently present.

Note: Kruijt (1989,1996), in his monographic treatment of Sapium, had removed some African and EastAsian species from Sapium and transferred these to Hurusawa's genus Shirakia (= Neoshirakia). However, as the type species Shirakiajaponica according to Esser (1998) differs from the other species in several respects, it was necessary to establish a new genus (Shirakiopsis) for those other species. This is confirmed by wood anatomy: the wood of Shirakiopsis differs from that of Neoshirakiajaponica and Sapium by the presence of large silica bodies in the ray cells, and the absence of crystals, features also present in Sclerocroton.

Spirostachys Sonder - Fig. 55,56 An African genus of 2 species.

Material studied: S. africana Sond.: sw. Africa: (PFPw 2300-0170, USw 31361A); Angola: Dechamps et al. (Tw s.n.); E. Africa: (Berlin s.n.); S. Africa: (PFPw - Ink. 2300) - S. venenifera Pax: (K-Jw 10-1954).

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Generalfeatures: Heartwood dark brown with fine yellowish streaks, sapwood yellow; aromatic; texture fine; heavy; density c. 1.00.

Microscopicfeatures: Growth rings faint, poorly defined, occasionally boundaries com­ posed of radially compressed fibres, and very narrow vessels; the light and dark zones as seen in transverse seetion are not related to growth rings. Vessels diffuse, 20-50% solitary, remainder in radial multiples of 2-4(-6), often in twin multiples or in clusters; 45 (21-82) per sq. mm. Outline oval, diameter 50-80 (110) !Am; vessel element length 470 (270-750) !Am. Perforations simple, intervessel pits alternate, 7-9 !Am wide, oval to roundish or with angular borders, apertures often coalescent; vessel-ray pits of the same size as intervessel pits. Resin often present. Fibres non-septate, diameter 16-20 !Am, thin-walled, 3 !Am, in some sampies walls often gelatinous; pits very smalI, simple, mostly in radial walls; length 795 (560-1030) !Am. F/V ratio 1.80. Rays generally uniseriate, occasionally biseriate, or locally biseriate, 12-17 per mm. Composed of procumbent cells interrningled with square cells of the same height (20 !Am), occasionally with a marginal row of short upright cells; usually 200-500 !Am high, width about 18 !Am. Disjunctive cell walls frequently present. Large, single rhombic crystals numerous in both cell types. Parenchyma apotracheal in irregular, often interrupted bands 1 to 2 cells wide or as diffuse strands, 6-10 per mm. Strands of 4-8 cells. Crystals occasionally present.

Note: The wood of Spirostachys africana (Tambootie in South Africa), being a timber of commercial value, was described by several authors (Burtt Davy 1929; Ferreirinha 1955; Kribs 1968; Kromhout 1976; Norrnand & Dctienne 1992). The last mentioned authors stressed in their paper the close similarity between wood of S. africana and Excoecaria parvifolia not only in anatomical respect but also in technologie al char­ acters. They suggest to reduce the two taxa to one. Similarity of important differenti­ ating anatomical features, like the size of pits, structure of rays and cellular contents, occurs also between the two species of Spirostachys described here and Excoecaria agallocha. Different opinions were held by students of the family like Bentham and Hooker (1880), Mueller Argoviensis, and Pax and Hoffmann (1912) about the position of Spiro­ stachys in relation to Excoecaria. This indicates the difficulty to define the genera. Though Esser (1994) obviously appeared in favour of merging both genera, he did not actually do so in this paper, nor in his contribution to Radcliffe-Smith's (2001) Genera Euphorbiacearum not having studied the type material (pers. comm.). Anyhow, wood anatomy strongly supports inclusion of Spirostachys in Excoecaria.

Stillingia Garden ex L. - Fig. 57 A genus of 30 species with a main distribution in the New World from the USA (Kansas) to Argentina. Three (?) species of the series Dichotomae with a wider distri­ bution, including Mauritius, Fiji and a few islands in the Malaysian archipelo.

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Material studied: S. aquatica Chapm.: USA, S. Carolina: S.w. Leonard 2652 (herb. mat.) - S.lineata (Lam.) Muell. Arg. subsp. pacifica (Muell. Arg.) Steenis: Fiji: Bryan Jr. 102 (MADw 24587). General features: Shrub with beige, straight-grained, fine-textured, moderately hard wood.

Fig. 55-58. Tribe Hippomaneae. - 55 & 56. Spirostachys africana, Dechamps et al. (Tw s.n.). - 55: Transverse seetion. - 56: Tangential seetion. - 57. Stillingia lineata subsp. pacifzca, Brian Ir. 102. Transverse seetion. - 58. Triadica cochinchinensis, China. For. Res. Inst. 58. Transverse seetion with growth ring margin of a few rows of radially compressed fibres. - Sc ale bars: 55-58 = 100 I-lm.

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Microscopic features: Growth rings vague. Vessels diffuse, 24% solitary, remainder in radial multiples of 2-3, and in clusters; 29 (21-40) per sq. mm. Outline oval, diameter 30-70 !lm; length of vessel element 420 (300-550) !lm. Perforations simple, intervessel pits 5-8 !lm, with slightly angular borders; vessel-ray pits similar, occasionally elongate, with slightly reduced borders. Fibres non-septate, rarely with spirals, diameter 14-18 !lm, walls 2-3 !lm thick, often gelatinous; minute bordered pits restricted to radial walls. Length 870 (720-980) !lm. FIV ratio 2.1. Rays exclusively uniseriate; 14-16 per mm. Composed either of exclusively upright cells or of irregularly distributed procumbent, square and upright cells. Width c. 20 !lm, height 100-450!lm (2-10 cells). Large rhombic crystals frequently present in all types of ray cells. Parenchyma apotracheal, in patches and in one-cell-wide, irregular, often interrupted bands. Strands of 2-4 cells; some cells septate. No contents.

Note: The description is based on the mature wood of S. lineata. The juvenile wood of S. aquatica, a rheophyte, differs by the following characters: wide fibres with extremely thin walls, scarcity of parenchyma, absence of crystals in ray cells, and preponderance of elongate vessel-ray pits. In a phylogenetic analysis by Esser et al. (1997) Stillingia comes close to Falconeria and Sapium, and also fairly close to Senejelderopsis. The occurrence of numerous large crystals in the rays and the occasional presence of 2-celled parenchyma cells point to a certain relationship with Sapium. Falconeria differs mainly by the distribution of crystals in the axial parenchyma. Senejelderopsis decidedly differs by the presence of both crystals and silica, and a different type of vessel-ray pits.

Triadica (Lour.) Muell. Arg. - Fig. 58 A genus of 3 species in E. Asia and Malaysia.

Material studied: T. cochinchinensis LoUf.: China: For. Res. lust. 58 (Tw 41821); Malaysia: Phytochem. Survey KL3168 (Lw) - T. sebifera (L.) Small: China: For. Res. lust. 1384 (Tw 41822); Russia, Georgia: (LEw s.n.).

Generalfeatures: Medium-sized trees with moderately hard, whitish wood, straight­ grained.

Microscopic features: Growth rings clearly demarcated by rows of radially compressed fibres and slightly smaller latewood vessels. Vessels diffuse, 30-50% solitary, remainder in radial multiples of2-3, occasionally in longer or in twin rows; 4 (1-6) per sq. mm. Outline oval, diameter (60-) 100-150 !lm; vessel element length 707 (500-910) !lm. Perforations simple, intervessel pits alternate, polygonal, 8-10(-12) !lm; vessel-ray pits of the same size or slightly larger than the intervessel pits, with slightly reduced borders. Fibres non-septate, diameter 20-25 !lm, walls 2 !lm thick, occasionally gelatinous; pits numerous, restricted to radial walls. Length 1160 (800-1500) !lm. FIV ratio 1.65.

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Rays generally uniseriate, but biseriate or locally biseriate rays also present; 13-15 per mm. Composed of procumbent, square or an intermediate type of cells, upright cells rather scarce. Height mostly about 600 f-lm, but also up to 1700 f-lm (54 cells), width 16-25 f-lm. Perforated ray cells noticed. Rhombic crystals rare. Narrow laticifers oc­ casionally present. Parenchyma apotracheal, in one- to two-cell-wide, undulating and often interrupt­ ed bands; about 8-10 per mm. Strands of 4-8 cells. Rhombic crystals occasionally present.

Note: In Esser's papers (1998, 1999b, 2002) the history ofthe genus is given. He con­ siders Triadica as a separate genus within a group of genera c10sely related to Sapium. The wood structure also shows a c10se similarity to Sapium.

Tribe 3. PACHYSTROMATEAE (Pax & K. Hoffrn.) Pax

A South American tribe consisting of the monotypic genus Pachystroma.

Pachystroma Muell. Arg.

Material studied: No sample was available. The description of Pachystroma ilicifolium Muell. Arg. is taken from Mainieri and Chimelo's paper (1989).

Generalfeatures: A fine-textured, light coloured, slightly glossy, rather heavy wood; density 0.80.

Microscopic features: Growth rings indicated by narrow zones of darker colour with ftattened thicker-walled fibres. Vessels diffuse, 20% solitary, the remainder in multiples of 2-4, 7-23 per sq. mm. Outline oval, diameter 20-80 f-lm. Perforations simple, intervessel pits alternate, large, 7-13 f-lm wide; vessel-ray pits simple or bordered, roundish. Thin-walled tyloses present. Fibres with medium-thick walls; bordered pits small and numerous. Rays usually uniseriate, seldom locally biseriate, heterocellular, 9-16 per mm; height 100-200 f!m. Parenchyma apotracheal in c10sely spaced, rather regular, 1-3-cell wide, tangential bands. Contents: numerous crystals.

Note: The wood structure of Pachystroma resembles that of Hura in a number of char­ acters like the large intervessel pits, the large, round vessel-ray pits, the short rays and the frequent occurrence of crystals in parenchyma cells. A relationship with Stillingia, as suggested by Baillon (1865), is supported by features like narrow vessels and low rays, but contradicted by the occurrence of crystals in parenchyma cells and by the larger intervessel pits.

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Tribe 4. HUREAE Dumort.

An American tribe of four genera of trees and shrubs. Only Hura was studied here because no material of the other three genera was available.

Hura L. - Fig. 59-61 A genus of 2 species restricted to Mexico, the West Indies, and tropical South America.

Material studied: H. crepitans L.: Suriname: Stahel52, B.B.S. 7, BW 6275; Venezuela: USw 4219,9871; Brazil: Maas et al. P16342, Maguire et al. 51842 - H. polyandra Baill.: Mexico: King & Soderstrom USw 27005.

General features: Large, tall trees, the wood rather coarse, grayish brown or beige, without differentiation in heartwood and sapwood, soft to very soft, straight or cross­ grained; density 0.30-0.50.

Microscopic features: Growth rings faint, boundaries indicated by a few rows of radi­ ally compressed fibres. Vessels solitary and for 50-60% in radial multiples of 2-4, occasionally in much longer chains of up to 11 vessels; 2 (0-6) per sq. mm. Outline round to oval, diameter 100-200(-330) !lm, vessel element length 525 (400-730) !lm. Perforations simple, intervessel pits alternate, very large, the border roundish or angular, 16-20 !lm wide; vessel-ray pits large, roundish, irregularly distributed, with strongly reduced borders. Thin-walled tyloses often present. Fibres non-septate, walls thin, c. 2 !lm thick, often gelatinous, diameter 20-36 !lm, up to 40 !lm in H. polyandra, some with intrusive cavities. Pits very small with aminute border, restricted to radial walls; length 1280 (1300-1430) !lm. F/V ratio 2.44. Rays exclusively uniseriate, 6-7 per mm, slightly heterocellular to almost homocel­ lular, composed of procumbent cells of various sizes, the cells in the centre of the ray longest, horizontally 80-160 !lm, at the margin shorter and resembling square cells; ray height 150-500 !lm, width 18-24 !lm. Intercellular spaces conspicuous. Parenchyma apotracheal, in numerous 1-3-cell-wide, straight or interrupted or zig­ zag bands, also paratracheal as narrow vasicentric rings. Strands of2-4 very large cells. Contents: large rhombic crystals, solitary or several, in non-chambered or chambered parenchyma cells.

Note: The wood of Hura is distinguished from that of most other genera of this sub­ family, and of the other subfamilies as weIl, by the almost homocellular, low rays. How­ ever, the dimensions of the ray cells, in particular the height of the cells and the ten­ dency to develop square-like cells at the margins, are features also present in some other genera of the Euphorbioideae. Solereder (1899) mentioned the occasional presence of scalariform perforations.

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Fig. 59-61. Tribe Hureae: Hura crepitans. - 59 & 60: USw 9871. - 59: Transverse section with narrow boundaries of radially compressed fibres. - 60: Tangential section showing inter­ cellular cavities between ray cells, and crystals in chambered and non-chambered parenchyma cells (arrowheads). - 61. Maas et al. P16342. Tangential seetion. - Scale bars: 59 =250 11m; 60 = 50 11m; 61 = 100 11m.

Tribe 5. EUPHORBIEAE Blume

A tribe of 10-12 genera. The exact number of genera depends on whether Chamaesyce and Elaeophorbia are regarded as distinct genera or are to be included in Euphorbia. Chamaesyce is often treated as a subgenus of Euphorbia, e.g. by Carlquist (1970) in his contribution to the wood anatomy of a number of Euphorbia species. Elaeophorbia, an African tree with a cactus-like habit, was treated by Webster (1994) as a synonym of Euphorbia. In the present paper both taxa are treated as independent genera following Koutnik (1987) and Radcliffe-Smith (2001).

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The anatomy shows a considerable variation particularly in the genus Euphorbia with its numerous growth fonns, varying from herbs and dwarf shrubs to large trees with a cactoid habit. In contrast to the other tribes, cell inclusions like silica and crystals are rarely present, whereas laticifers, except in Anthostema and Synadenium, are common, often being a striking feature of the rays.

Anthostema A. Juss. - Fig. 62 A palaeotropical genus of 3 species, confined to tropical West Africa and Madagas­ car. Material studied: A. aubryanum Boiss.: W. Africa, Gabon: (CTFT 15658).

Generalfeatures: Light brownish wood with poorly differentiated sapwood and heart­ wood. Lysigenous cavities present, designated as "alveoles alaticiferes" by Nonnand and Paquis (1976).

Microscopic features: Growth rings present, irregular, characterized by narrow bounda­ ries of radially compressed fibres. Vessels diffuse, about 40% solitary, the remainder in radial multiples of 2-4; 3 (0-9) per sq. mm. Outline elliptic, diameter 100-150(-180) !Am; vessel element length 725 (630-900) !Am. Perforations simple; intervessel pits alternate, round to angular, 9-14 !Am; pits to ray cells large, elliptic, in opposite or alternate arrangement, with strongly reduced borders. Thin-walled tyloses occasionally present. Fibres non-septate, the walls 2-4 !Am thick, often gelatinous, diameter 28-38 !Am; pits very smalI, simple, restricted to radial walls. Length 1438 (1259-1700) !Am. F/V ratio 1.98. Rays uniseriate; 10 per mm. Heterocellular, procumbent cells rather high and short, upright cells up to 100 !Am high. In some rays various cell types irregu1ar1y distributed, in others with a central part of procumbent cells and margins of a few rows of upright and square cells; cells often rounded (in TLS) and intercellular spaces striking; width c.20 !Am, height mostly about 600 (100-1400) !Am. Small silica grains present. Lati­ cifers not noticed. Parenchyma apotracheal, in numerous one- to two-cell-wide, often interrupted bands, 7-8 per mm, and in isolated diffuse strands. Strands of 4-6, occasionally 2 cells. Small silica grains infrequently present.

Note: Hurusawa's (1954) suggestion of a relationship between Anthostema and Dale­ champia (subfamily Acalyphoideae) is reflected in wood anatomy, except for the pres­ ence in Dalechampia of crystals in ray and parenchyma cells as contrasted with the silica inclusions in Anthostema.

Dichostemma Pierre - Fig. 63-65 A genus of 3 species of tropical West Africa.

Material studied: D. glaucescens Pierre: ZaIre: Dechamps 109 (Tw 8500).

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Fig. 62-65. Tribe Euphorbieae. - 62. Anthostema aubryanum, CTFT 15658. Transverse seetion. - 63-65. Dichostemma glaucescens, Dechamps 109. - 63: Transverse seetion. - 64: Tangential seetion showing heterocellular, uniseriate rays; rhombic crystals in a parenchyma cell (arrow­ heads). - 65: Radial seetion showing large, irregular vessel-ray pitting. - Scale bars: 62 & 64 = 100 11m; 63 = 300 11m; 65 = 50 11m.

Generalfeatures: A light brown, moderately light wood.

Microscopicfeatures: Growth rings distinct, due to marginal bands of radially ftattened fibres with gelatinous walls.

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Vessels diffuse, 25% solitary, remainder in radial multiples of2-3(-5), clusters rare, no twin rows noticed; 9 (4-11) per sq. mm. Outline elliptic, diameter (100-)150-200 firn, vessel element length 710 (550-890) firn. Perforations simple, intervessel pits angular, 8-9 firn; vessel-ray pits crowded, partly similar to the intervessel pits, but also large, elliptic or renifonn, with strongly reduced borders. Fibres non-septate, about 20 firn wide, walls 3 firn thick, pits numerous, minutely bordered, restricted to radial walls. Length 1000 (900-1350) firn. F/V ratio 1.55. Rays uniseriate, seldom 2 cells wide over a short distance; 16 (14-17) per mm. Composed of square and procumbent cells, most cells square with transitions to 70 firn high upright cells at the margins but also in the centre. Width 16-20 firn, height up to 1000 firn. Intercellular spaces conspicuous. Laticifers present but extremely rare. Parenchyma in concentric, fairly regular, slightly wavy, one-cell-wide bands; 3 per mm. Strands of 2-8 cells. Rhombic crystals occasionally present.

Note: Anthostema and Dichostemma resemble each other in the irregular vessel-ray pits. They differ in fibre diameter and in cellular contents; in Anthostema silica is present in ray and parenchyma cells, in Dichostemma parenchyma cells occasionally contain rhombic crystals. Laticifers were noticed in Dichostemma, not in Anthostema.

Neoguillauminia Croizat - Fig. 70, 71 A monotypic genus of New Caledonia.

Material studied: N. cleopatra (Baill.) Croizat: New Caledonia: (WIBw 3650).

Generalfeatures: A fine-textured, hard, olive-brown, somewhat streaked wood; den­ sity c. 1.0.

Microscopic features: Growth rings absent or obscure. Vessels 20% solitary, remainder in radial multiples of 2-6 with a tendency to radial arrangement; frequency 5 (1-9) per sq. mm. Outline elliptic, diameter 120-200 firn, vessel element length 1060 (750-1400) firn. Perforations simple, intervessel pits al­ ternate, 10-12(-15) firn, with elliptic borders; vessel-ray pits elliptic to angular, large, 12-16 firn, with slightly reduced borders. Thin-walled tyloses present. Fibres non-septate, walls partly gelatinous, c. 6 firn thick, diameter 28-40 firn, intru­ sive cavities occasionaly present. Pits numerous, small with narrow borders, restricted to radial walls; length 1722 (1250-2225) firn. F/V ratio 1.6. Rays uniseriate, occasionally biseriate, 5-7 per mm. Most cells square or upright, procumbent cells of the same height as square cells, structure irregular. Width 30 firn, height 1-10 cells (120-1300 firn). Large rhombic and elongate crystals frequently present in all types of ray cells, often several in a cell. Intercellular spaces striking. Nar­ row laticifers present, but scarce. Parenchyma apotracheal, in one- to two-cell-wide, rather straight concentric bands, number of bands c. 5 per mm. Strands of (2-)4(-6) cells.

Note: The wood structure of Neoguillauminia with its large intervessel pits and banded parenchyma shows more affinities to Anthostema and Dichostemma than to Euphorbia, despite the structural diversity in the latter genus.

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Fig. 66-69. Tribe Euphorbieae: Chamaesyce. - 66 & 67. C. celastroides, Stern & Herbst 514. - 66: Transverse seetion. - 67: Tangential seetion. - 68. C. halemanui, Carlquist 1796. Transverse seetion showing vessel clusters. - 69. C. multiformis Var. microphylla, Webster et al. 13803. Tangential section. - Scale bars: 66 & 67 = 100 !lffi; 68 =300 !lffi; 69 = 100 !lID.

Chamaesyce Gray - Fig. 66-69 A cosmopolitan genus of about 250 species of herbs, subshrubs to shrubs or small trees. Material studied: C. articulata Britt.: Guadeloupe: Rollet 1098 (CTFf 28478) - C. cel­ astroides (Boiss.) Croiz. & Degener: Hawaii, Kauai: Stern & Herbst 514 - C. hale-

Downloaded from Brill.com10/09/2021 12:24:23AM via free access 52 IAWA Journal, Vol. 26 (1), 2005 manui (Sherff) Croiz. & Degener: Hawaii, Kauai: Carlquist 1796 - C. hypericijolia (L.) Millsp.: USA, Florida, W. Summerland Key: Hayden 2050 (URV) - C. multijormis (Hook & Am.) Croiz. & Degener var. microphylla (Boiss.) Degener & 1. Degener: Hawaii, Oahu: Webster et al. 13803 - C. nutans (L.) Small: USA, Maryland, Col­ lege Park: Hayden 06 (DRV) - C. remyi (A. Gray ex Boiss.) Croizat & Degener var. remyi: Hawaii, Kauai: Stern & Herbst 2938 (FLASw) - C. rockii (Forbes) Croiz. & Degener: Hawaii, Oahu: Webster et al. 13820 - C. sparsijiora (A. Heller) Koutnik: Hawaii, Kauai: Stern & Herbst 465.

Generalfeatures: Wood rather soft to moderately hard, yellowish brown. In C. celas­ troides brown heartwood present.

Microscopic features: Growth rings often absent, if present faint, indieated by bounda­ ries of eompressed thieker-walled fibres. Vessels 5-10% solitary, the remainder in radial multiples of2-8(-12), often in twin rows and clusters, diffuse, with a tendeney to radial arrangement; very numerous, 70-200 per sq. mm. Outline roundish to elliptic, often angular, diameter mostly 20-40 flm, walls about 4 flm thiek, vessel element length 484 (390-560) flm. Perforations simple, intervessel pits 5-10(-12) flm round to elliptie to sealariform; vessel-ray pits roundish to elongate, ofthe same size as the intervessel pits, with slightly redueed bor­ ders. In C. multijormis some vessels eontaining resin. Fibres non-septate, diameter 10-24 flm, walls 2-4 flm thiek, oeeasionally with ge­ latinous walls. Small bordered pits in radial and tangential walls. Length 760 (627-906) flm. FIV ratio 1.57 (1.40-1.66). Rays exclusively uniseriate or partly bi- and triseriate; 15-19 per mm, heteroeel­ lular, eomposed of proeumbent, square and upright eells; in small samples preponder­ anee of upright eells, proeumbent eells few, in the larger sample of C. articulata truly proeumbent eells more numerous, distribution irregular. Width 10-30 flm, up to 100 flm in rays eontaining latieifers, height mostly 300-500 flm, up to over 1000 flm in C. ar­ ticulata, the latter often vertieally fused. Perforated ray eells oeeasionally present. Lati­ eifers notieed in several samples, oeeasionally two to three in the same ray, the tubes narrow, surrounded by numerous proeumbent eells. Parenehyma searce, paratraeheal as ineomplete, one-eell-wide rings and apotraeheal as isolated strands and in narrow bands. Strands of 2-4 eells.

Note: Chamaesyce is often eonsidered as a subgenus of Euphorbia (Pax & Hoffmann 1931; Carter in Carter & Smith 1988), but following Koutnik (1987) and Webster (1994) it is treated here as a separate genus, closely related to Euphorbia. Wood anatomy ean­ not (yet) supply arguments for or against this. The material studied is too limited eon­ sidering the large number of speeies in both genera, and the great variety in life forms. Anyhow a close resemblanee exists in wood strueture, in partieular if eomparing Chamaesyce with shrubby Euphorbia speeies.

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Fig. 70-74. Tribe Euphorbieae. - 70 & 71. Neoguillauminia cleopatra, WIBw 3650. -70: Tan­ gential section; short heterocellular rays. - 71: Radial section; cells with one or more variously shaped crystals. - 72-74. Elaeophorbia grandifolia, CTFT 19818. -72: Transverse seetion with few, narrow vessels. - 73: Tangential seetion showing two rays with laticifers in enlarged part. - 74: Radial seetion with vessel-ray perforation and large vessel-ray pits. - Scale bars: 70,73 & 74 = 100 ~m; 71 =50 ~m; 72 = 240 ~m.

Elaeophorbia Stapf - Fig. 72-74 A genus of 4 species, restricted to tropical and South Africa. Material studied: E. grandifolia (Haw.) Croizat: W. Africa, Congo: (CTFf 19818).

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Generalfeatures: Colour whitish, wood soft, straight-grained, Microscopic features: Growth rings faint. Vessels diffuse, for the greater part (90%) in radial multiples of 2-10, also in clus­ ters, but with a tendency to radial arrangement; 4.5 (0-10) per sq. mm. Outline elliptic, diameter 60-100 !Am, vessel element length 945 (625-1230) !Am. Perforations simple, intervessel pits large, elliptic, in horizontal or scalariform arrangement, 30-80 !Am; oc­ casionally a few smaller pits present; vessel-ray pits scalariform, similar to intervessel pits, but with strongly reduced borders. Fibres non-septate, diameter 32-45 !Am, walls 3.5 !Am thick, for the greater part gelatinous. Pits bordered, very small, 3 !Am, restricted to radial walls. Length 1584 (1200-2150) !Am. FIV ratio 1.66. Rays uniseriate, locally 2 cells wide; 9 (8-11 )per mm. Strongly heterocellular, pro­ cumbent cells scarce and relatively high, upright cells up to 200 !Am high. Width 20-30 !Am; height 300-2000 !Am, the highest rays vertically fused. Perforated upright cells present. Laticifers present in locally enlarged rays. Parenchyma apotracheal in l-seriate, often interrupted bands, difficult to recognize on cross sections because the cell diameter is equal to the fibre diameter and the walls are of the same thickness. Strands of 2-4 cells.

Note: Webster (1987, 1994) considered Elaeophorbia as a synonym of Euphorbia. Dechamps (pers. comm.) stated that Elaeophorbia is quite different in its habit from Euphorbia and Normand and Paquis (1976) treated the wood as a distinct genus. Smith (in Carter & Smith 1988) also recognized the genus as different from Euphorbia. The relatively long vessel elements and the long fibres are not in accordance with Eu­ phorbia. They might be considered indeed as features in favour of a separate genus (Mennega 1999).

Euphorbia L. - Fig. 75-81; Table 4 A very large genus of over 1000 species, cosmopolitan. Chiefty herbaceous, but also containing shrubs, small and large trees, often with a cactoid habit.

Material studied: E. atropurpurea Brouss.: Islas Canarias: Lindeman 7102 - E. bal­ samifera Ait.: Islas Canarias: Lindeman 7128 - E. calycina N. E. Br.: Angola: Dechamps et al. 1296 (Tw 28608) - E. cotinifolia L. subsp. cotinoides (Miq.) Christenhusz: Guyana: Jansen-Jacobs et al. 4868 - E. dendroides L.: Italy, Calabria: Mennega 701; Malta: Kramer & Westra s.n. - E. ingens E. Mey. ex Boiss.: S. Africa: PFPw 2296; ZaIre, Katanga: Malaisse 10025 (Tw 38723); Dechamps (Tw 24209) - E. poissonii Pax: Togo: Kersting 414 - E. schlechtendalii Boiss.: Mexico, Sinaloa: Webster et al. 15650 - E. tirucalli L.: Angola: Dechamps 1212 (Tw).

Generalfeatures: Usually light coloured yellowish or greyish brown wood, in some species with dark brown heartwood; lysigenous cavities occasionally present; straight­ grained, fine-textured, soft to hard; density 0.37-1.00.

Microscopic features: Growth rings not always present, if present characterized by boundaries of radially compressed thicker-walled fibres.

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Fig. 75-78. Tribe Euphorbieae: Euphorbia. - 75 & 76. Euphorbia calycina, Dechamps et al. 1296. -75: Transverse seetion. -76: Tangential seetion showing scalariform intervessel pitting. - 77 & 78. Euphorbia cotinifolia subsp. cotinoides, Jansen-Jacobs et al. 4868. - 77: Transverse seetion. - 78: Tangential seetion; intervessel pitting alternate; widened ray with laticifer. - Scale bars: 75 = 240 ~m; 76-78 = 100 ~m.

Vessels 3-15% solitary in most species; however, in E. baZsamifera, E. schZechten­ daZii and E. tirucalli 30-50% solitary, the remainder in often long radial multiples, clusters and twin-rows with a tendency to radial arrangement or in patches; 10 (5-19) per sq. mm, except for E. dendroides with 37 (20-48) per sq. mm. Outline angular or

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Fig. 79-81. Tribe Euphorbieae: Euphorbia. - 79. Euphorbia ingens: PFPw 2296. Radial seetion showing scalariform vessel-ray pitting. - 80. Euphorbia cotinifolia subsp. cotinoides, Jansen­ Jacobs et al. 4868. Radial section showing half-bordered vessel-ray pits. - 81. Euphorbia poissonii, Kersting 414. Radial section showing latex tube with surrounding cells. - Scale bars: 79 = WO f..tm; 80 & 81 =50 f..tm . roundish to elliptic, thin-walled, diameter 30-80(-120) !!m, vessel element length 440 (336-610) !!m. In E. cotinifolia some vessels with spiral thickenings noticed. Perfora­ tions simple (occasionally scalariform in narrow vessels of E. grandicornis (Uhlarz & Kunschert 1976)); intervessel pits exclusively scalariform or both scalariform and

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1 Table 4. Selected features in Euphorbia. 1 c~ Euphorbia Distribution Habit Vessels Fibres .... species ;:\:> number diam. element length pits diam. length FIV \:> in [lm in [lm in [lm in [lm 0 ~ E. atropurpurea Canary Isl. suce. shrub 16 ( 4-30) 20-45 390 (220-600) seal. up to 30 [lm 18-24 638 (430-770 ) 1.63 '" ----tll E. ingens South Afriea eaetoid tree 5 ( 2-12) 50-100 346 (270-450) seal. up to 100 [lm 26-38 886 (710-1030) 2.56 {j ;:- c E. oncoclada Madagasear eaetoid tree 10 ( 0-29) 50-100 590 (430-700) altem. 7-8 [lm 17-24 867 (650-1000) 1.47 .... ~ Downloaded fromBrill.com10/09/2021 12:24:23AM E. poissonii Togo eaetoid tree 8.5 ( 4-13) 40-60 336 (160-470) seal. up to 60 [lm 20-30 833 (700-1100) 2.54 Ei· "'"\:> E. schlechtendalii Mexieo shrubby tree 19 (16-23) 60-120 387 (250-500) altem. 9-15 [lm 12-16 735 (630-870 ) 1.90 ~

E. tirucalli Angola suee. tree 8 ( 3-15) 30-50 326 (160-480) altem. 8-10 [lm 16-20 630 (400-820 ) 1.93

* = Euphorbia candelabrum. via freeaccess

VI -.l 58 IAWA Journal, Vol. 26 (I), 2005 elliptic, or all alternate, rounded to elliptic, scalariforrn pits up to 100 /lm wide, extend­ ing over the complete wall-face, small pits 5-9 /lm wide. In E. cotinifolia, E. onco­ clada, E. schlechtendalii and E. tirucalli exc1usively small pits noticed; vessel-ray pits similar to intervessel pits, but with strongly reduced borders. Tracheids present in E. dendroides. Fibres generally non-septate, but septate fibres present in E. cotinifolia and E. tiru­ calli, walls thin to medium-sized, 2-4 /lm, occasionally gelatinous, diameter variable, in some species 16-20 /lm, in others 20-25 /lm, in most ofthe cactoid species (E. bal­ samifera, E. calycina, E. ingens and E. poissonii) up to 38 /lm wide and thin-walled, pits numerous, very small, simple or with minute borders, restricted to the radial walls or present in both walls. Length 845 (580-1000) /lm. F/V ratio 1.92 (1.47-2.56). Rays generally uniseriate and occasionally biseriate over a small portion of the height, 2-3 cells wide in E. cotinifolia, up to 5 cells wide in E. schlechtendalii; often conspicuously widened around laticifers; 17 (13-20) per mm. Both types heterocellular with irregular distribution of square, upright and procumbent cells, the latter type scarce and the cells radially relatively short. Width 30-50(-70) /lm, height mostly 200-800 /lm, but up to 1800 /lm. Perforated ray cells present. Laticifers always present, narrow to c. 80 /lm wide, surrounded by few to severallayers of irregular, elongate procumbent cells; sometimes more than one in the same ray. Rare rhombic crystals noticed in E. bal­ samifera, numerous in E. hierosolymitana (Fahn et al. 1986). Parenchyma apotracheal diffuse or in narrow, often interrupted bands and scanty paratracheal as isolated cells or as narrow, incomplete rings. Strands of 2-4 cells, with a predominance of 2 cells; cells occasionally septate.

Note: The very large, cosmopolitan genus Euphorbia with over 1000 species is chiefly herbaceous, but dwarf shrubs, shrubs, low and rather tall trees, some with a cactoid habit, also occur. Among the woody members of the genus a considerable variation ex­ ists in overall wood structure, partly reflecting the different habits and habitats. Though the structural variation comprises all elements, the most striking variation occurs in vessel characters, in particular the pitting. In contrast to Carlquist (1970), who noted the prevalence of 4-celled parenchyma strands, in my material 2-celled parenchyma strands were common in all species. The material studied for this paper comprises partly the same species as those stud­ ied by Carlquist (1970) supplemented by four cactoid African species, the shrubby E. cotinifolia of tropical South America and the shrubby mediterrane an E. dendroides. Schweingruber (1990) treated the wood structure of three more shrubs from the Canary Islands, resembling the wood structure of E. dendroides. Fahn et al. (1986) described the wood of the east mediterranean dwarf shrub E. hierosolymitana, characterized by very wide rays. In general data from the literature are in agreement with the genus description given above. The mediterranean species, for instance, resemble each other except for differences in number and size of the vessels, and in the width of laticifer­ containing rays. A noteworthy distinction exists between the cactoid and non-cactoid species in the pitting ofthe vessels, respectively large and scalariforrn, and moderately small with enc10sed apertures.

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, As mentioned in the note accompanying the description of Chamaesyce, no con­ sensus exists on the delimitation of the genus Euphorbia. Carlquist (1970) included in his overview several species from Hawaii which are treated in the present paper as belonging to Chamaesyce.

Pedilanthus Neck. ex Poit. - Fig. 82, 83 Neotropical genus of c. 15 species of succulent shrubs, all except one confined to Mexico and adjacent Central America.

Material studied: P. tithymaloides (L.) Poit.: Cultivated: Christenhusz 81, twig sampie of 4 mm diameter.

Microscopic features: Growth rings absent. Vessels diffuse, mainly in radial multiples of 2-4 and in clusters, c. 50 per sq. mm. Outline angular, diameter 25-40 !Am; vessel element length 380 (210-600) !Am. Perfora­ tions simple, intervessel pits large, elliptic, almost reaching from wall to wall, scalari­ form; vessel-ray pits large, gash-like, scalariform, with strongly reduced borders. Fibres non-septate, walls about 2 !Am thick, diameter c. 16 !Am; pits minute, simple, confined to radial walls. Length 757 (510-950) !Am. FIV ratio 2.0. Rays uni- and biseriate; numerous. Juvenile with exclusively upright cells, 100-130 !Am tall. Width 20-40 !Am, height up to 1 mm (10 cells). Several rays with one or more thin-walled laticifers, locally slightly expanded. Parenchyma paratracheal, incompletely vasicentric and apotracheal in short uniseri­ ate bands and diffuse. Strands of 2-4 cells.

Note: The wood resembles in many respects that of the cactoid species of Euphorbia as well as that of Synadenium, but differs from the wood of the latter by the numerous laticifers.

Synadenium Boiss. - Fig. 84-86 A genus of about 19 closely related species of East and southem tropical Africa (Carter & Smith 1988).

Material studied: Synadenium sp.: E. Africa: Scheffier 6 (RBHw).

General features: A light coloured, very light wood.

Microscopic features: Growth rings not observed. Vessels diffuse, 10% solitary, the remainder in multiples of 4-5 and in clusters; 3-4 (0-9) per sq. mm. Outline angular, diameter 50-80 !Am, vessel element length 620 (390-875) !Am. Perforations simple, intervessel pits scalariform or opposite, 30 !Am or more wide; vessel-ray pits mostly large and scalariform, with strongly reduced bor­ ders. Fibres non-septate, diameter 30-60 !Am, walls thin, 2 !Am, but often thicker with a gelatinous layer. Pits minutely bordered, restricted to radial walls. Length 1100 (930- 1350) !Am. FIV ratio 1.77.

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Fig. 82-86. Tribe Euphorbieae. - 82 & 83. Pedilanthus tithymaloides, Christenhusz 81. - 82: Transverse section. - 83: Tangential section showing two latex tubes. - 84-86. Synadenium sp., Scheffler 6. - 84: Transverse section. - 85: Radial section showing different types of ray cells. - 86: Tangential section showing latex tube (arrowheads). - Scale bars: 82 & 85 = 100 !olm; 83 & 86 = 50 !olm; 84 = 250 !olm.

Rays uniseriate or biseriate over aheightof2-4 rows of cells; 11 perrnm. Heterocel­ lular, most cells upright, square cells few, procumbent cells almost absent; perforated ray cells with irregular perforations present. Width 40 !-lm, height up to 2300 !-lm; inter­ cellular spaces obvious. Laticifers not noticed.

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Parenchyma diffuse; the distribution difficult to observe, the cell diameter being equal to the fibre diameter. Strands of 2 cells, occasionally one-celled and septate.

Note: The wood structure of the single specimen available shows many affinities to succulent Euphorbia and Pedilanthus, e.g. in the intervessel pits, parenchyma strands of 2 cells, and the absence of crystals. Synadenium differs by the absence of laticif­ ers. However, Rudall (1987) recorded the presence of non-articulated laticifers in the genus.

DISCUSSION Relationships within the subfamily Stomatocalyceae In Stomatocalyceae two subtribes are recognized. Biseriate rays are common in Stomatocalycinae, while in subtribe Hamilcoinae (only genus Nealchornea represented here) they are predominantly uniseriate (Table 2). They are often high due to vertical fusion, whereas in the other tribes rays are usually uniseriate or only over a short range biseriate and ranging from low to high. The tribe Stomatocalyceae shows greater ana­ tomical affinity to Crotonoideae than to Euphorbioideae. My results are in agreement with the treatment of the Euphorbiaceae by Metcalfe and Chalk in their Anatomy of the Dicotyledons (1950). In this work, the system of Bentham and Hooker was fol­ lowed, consequently Euphorbioideae are treated under Crotonoideae. Crotonoideae and Acalyphoideae are considered to be closely related; this is in accordance with pollen morphological features of Plagiostyles and Pimelodendron, wh ich are considered to be closer to Bernardia (Acalyphoideae) by Punt (1962). The suggestion that the tribe does not fit weIl in Euphorbioideae is in accordance with results of a molecular study by Wurdack and Chase (1999) who stated in abrief note that by excluding Stomatocalyceae, Euphorbioideae becomes monophyletic. The results ofPark and Backlund (2002), analysing the cyathium-bearing Euphorbieae, point towards a similar conclusion.

Hippomaneae In the largest tribe, Hippomaneae, which on the whole is quite uniform, two subtribes are present: Carumbiinae and Hippomaninae. In the Carumbiinae the only genus is Homalanthus, according to Webster (1994). In a consensus cladogram based on mor­ phological characters, Homalanthus is placed at the base of this tribe (Esser 1997). Con­ sequently, also in Radcliffe-Smith (2001) it is considered to form a subtribe of its own. In its structure it does not show any special features to support this concept (Table 2). The wood is similar to that of Sapium. In Hippomaninae, Hippomane (the type genus) as weIl as Grimmeodendron and Pleradenophora differ from other genera by low, almost homocellular rays. In the other genera rays are strongly heterocellular. Actinostemon, Gymnanthes p.p., Pseudosenefeldera and Rhodothyrsus share a remarkable radial zonation altematingly with and without vessels (Table 2). In these

Downloaded from Brill.com10/09/2021 12:24:23AM via free access 62 IAWA Journal, Vol. 26 (1), 2005 taxa, together with Shirakiopsis, very large silica bodies in numerous ray cells occur. Esser (pers. comm.) also points towards the striking similarity between these genera in their leaf morphology. Simultaneous presence of silica and crystals was noticed in Colliguaja, Gymnanthes p.p., Sclerocroton p.p., Senejelderopsis and in one species of Mabea. Maprounea stands apart by the occasional occurrence of scalariform vessel perfora­ tions, and by rather small intervessel pits contrasting with the small and large, irregular vessel-ray pits (see note under the generic description). Excoecaria and Spirostachys are very similar in both morphology and anatomy. Accordingly, taxonomists as weIl as anatomists have suggested to unite these genera, but to date this has not been done. The dismembering of Sapium initiated by Kruijt (1996), restricting the genus to the New World, was followed by Esser (1999b) who established several additional new genera, such as Balakata and Shirakiopsis, for species formerly included in Sapium. These two genera differ from Sapium by the presence of silica, whereas Sapium is characterized by the occurrence of crystals in ray cells. In Falconeria, another recently re-established genus, crystals occur in the axial parenchyma. Triadica, however, wh ich previously belonged in the Sapium alliance, is anatomically similar to Sapium. Actinostemon, Gymnanthes, and Sebastiania form another complex of related genera. Webster (1994) considered Actinostemon to be congeneric with Gymnanthes. This is only partly confirmed by the wood anatomy, due to the pluriformity of Gymnanthes. One species, G. klotzschianum (syn. Sebastiania klotzschiana), resembles Actinostemon in relevant characters such as the radial zonation of the vessels, and the large silica inclusions of the ray cells. Sebastiania sensu Esser is distinct in that it has large crystals in ray cells.

Pachystromateae and Hureae The two tribes Pachystromateae and Hureae share low, almost homocellular rays similar to the rays of Hippomane.

Euphorbieae The frequent occurrence of two-celled parenchyma strands is a feature of the whole tribe, except Neoguillauminia (Table 2). However, Euphorbieae is more variable than the other tribes. Two of the three subtribes recognised by Webster (1994), Anthosteminae and Neoguillauminiinae, show a greater structural similarity to Hippomaneae than to Euphorbiinae, e.g. by the presence of silica or crystals and by a similar type of incon­ spicuous latex tubes. In Euphorbiinae, on the other hand, cell inclusions are extremely rare. Laticifers usually are a striking feature here, being wider and more numerous than in the other tribes, except in Synadenium, a genus which resembles Chamaesyce, Elaeophorbia and Euphorbia in other aspects. The large and diverse genus Euphor­ bia, of which the woody species range from dwarf shrubs to large trees, often with a cactoid habit, also shows structural diversity, mainly in quantitative characters, but in intervessel and vessel-ray pitting as weIl.

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The anatomical results are in agreement with Steinmann and Porter's (2002) mo­ lecular studies of phylogenetic relationships in Euphorbieae, wherein monophyly of the tribe Euphorbieae is supported in addition to monophyly of the subtribes Anthosteminae, Neoguillauminiinae and Euphorbiinae. Within the latter subtribe four clades are recog­ nized, one representing Chamaesyce, another Synadenium and Pedilanthus (together with Endadenium and Monadenium, not studied here).

Relationships with other subfamilies There is hardly any evidence for a relationship between the wood ofEuphorbioideae and the wood ofPhyllanthoideae and Oldfieldioideae, as was discussed in previous papers (Mennega 1987; Hayden 1994). On the other hand, there is a close wood anatomical resemblance with Acalyphoideae and Crotonoideae. Hayden and Hayden (2000), in their treatment of Acalyphoideae, gave an excellent overview of the anatomical characteristics of this subfamily. A comparison of their data with the present study of Euphorbioideae shows, with few exceptions, a striking coincidence of features. Both subfamilies are characterized by the occurrence ofvessels in numerous small ra­ dial multiples and clusters of twin or dumbbell-shaped multiples. The unusual vessel dis­ tribution in radial zones noticed in several genera of Euphorbioideae is also present in Necepsia and Podadenia of Acalyphoideae. Vascular tracheids intergrading with nar­ row vessel elements are more frequent in Euphorbioideae. Exclusively scalariforrn perforations were found in the Acalyphoid genera Microdesmis and Panda. The position of the two genera in Euphorbiaceae is disputed. However, a combination of simple and scalariforrn perforations was recorded in 21 genera. In Euphorbioideae, by contrast, occasional scalariforrn perforations were only noticed in Maprounea and described for a young sampIe of Euphorbia grandicornis (Uhlartz & Kunschert 1975). Intervessel pit­ ting as weIl as vessel-ray pitting show the same diverse pattern in both subfamilies; with the exception ofthe very large pits in Euphorbia p.p., Hura and Sapium ofthe Euphor­ bioideae. Septate fibres, virtually absent in Euphorbioideae although occasionally observed in Euphorbia species, were present in four genera of Acalyphoideae. Otherwise fibres did not show important differences. Parenchyma distribution is alike in both subfamilies, i.e. mostly apotracheal as narrow more or less regular bands as weIl as diffuse-in-aggregates; paratracheal parenchyma is scanty or absent. Cell contents are frequently present as rhombic crystals, whereas silica inclusions are rare. Rays in Acalyphoideae show a wide range of variation and the same is true for Euphorbioideae, but the most frequent type in both subfamilies consists of narrow uni- to biseriate, heterocellular, relatively tall, often vertically fused rays. Certain ex­ ceptions such as the almost homocellular rays of Grimmeodendron, Hippomane, and Hura find their counterpart in the acalyphoid genus Leucocroton. The contents of ray cells, crystals as weIl as silica, is the same for both subfamilies; the remarkable co­ occurrence of silica and crystals as noticed in several genera of Euphorbioideae was recorded in Acalyphoideae in the genus Aparisthmium. Perforated ray cells is another feature shared by some genera in both subfamilies.

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A difference is found in the frequency of laticifers which are present in a great number of genera in Euphorbioideae, whereas in Acalyphoideae they are restricted to Dalechampia and Dicoelia. Lysigenous cavities, extensively treated in Hayden and Hayden's (2000) paper, occur also in several genera of Euphorbioideae, although without showing marked discrepancies in frequency among the tribes, unlike their striking presence in genera of the tribe A1chomeae of Acalyphoideae.

In conc1usion, a comparison of the two subfamilies only shows a marked difference in the presence of laticifers: scarce in Acalyphoideae and frequent in Euphorbioideae. This presence or absence of laticifers is in fact one of the discriminating characters between the two subfamilies. The wood of 44 genera of the subfarnily Crotonoideae studied (Mennega, unpub­ lished) generally conforms to that in the Acalyphoideae and Euphorbioideae as may be c1ear from the brief account given below. The pattern of vessel distribution is the same, although radial vessel zonation was not observed. Frequently multiples of 2-4 or more occur, mostly of medium-sized diameter but ranging from 50-290 !-lm, their frequency usually 10 per sq. mm or less, though also with a wide range from 4-150 per sq.mm. I observed occasional scalar­ iform perforations in Codiaeum, and they have also been recorded for twig material of Givotia (CutIer 1968). Intervessel pits ranged from 4-16 !-lm, large pits occurring in several genera, ray-vessel pits sirnilar or not, in the latter case pits often irregular or kidney-shaped. Ground tissue mostly consists of fibres with a wide lumen and rather thin walls, but thick-walled fibres are present in Leeuwenbergia, Micrandropsis, and in one spe­ cies of Pausandra. Septate fibres in juxtaposition to non-septate fibres were observed in Cnidoscolus, Jatropha and Manihot. Fibre length in several genera exceeds 2000 !-lm with a maximum in Leeuwenbergia of 2900 !-lm, whereas in Euphorbioideae the length seldom exceeds 1200 !-lm, except in ,Elaeophorbia, Anthostema and Neoguil­ lauminia. Parenchyma distribution resembles that in Euphorbioideae: mainly apotracheal in narrow, continuous or irregular, often waving bands; additionally some diffuse-in-ag­ gregates and diffuse; paratracheal vasicentric sometimes partly confluent occurs in Cnidoscolus, Croton and Manihot; crystals occasionally present, silica not observed. Rays are mostly uni- to biseriate, but rays up to 4 cells wide occur in several genera. The rays are heterogeneous, often with tall margins and often vertically fused. Per­ forated ray cells are also common. Cells frequently contain rhombic crystals, silica was observed in Annesijoa, Anomalocalyx, Glycydendron, Micrandra, Tetrorchidium; both crystals and silica were found in Cunuria and Sagotia. Lysigenous cavities are scarce and inconspicuous; they were noticed in Croton, Glycydendron and Micrandra. Latex tubes were observed in Baloghia, Croton and Glycydendron. As is the case with Acalyphoideae and Euphorbioideae the main difference between Crotonoideae and Euphorbioideae is to be found in the scarcity of laticifers in the Crotonoideae vs. their abundance in Euphorbioideae.

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CONCLUSIONS

Three out of the five tribes, viz. Hippomaneae, Pachystromateae, and Hureae, show a great deal of conformity in their anatomy. Stomatocalyceae stand apart by the combi­ nation of a scarcity of vessels and rays of a different structure, the latter being often biseriate, vertically fused and very high, characters more often present in Crotonoi­ deae. In contrast to the three preceding tribes, the Euphorbieae show a great diversity, mainly by the presence of silica or crystals and by the scarcity of laticifers in subtribes Anthosteminae and Neoguillauminiinae, whereas Euphorbiinae stand out by occasional scalariform vessel- and vessel-ray pitting, multiseriate rays, and the frequent occurrence of conspicuous laticifers. Wood structure indicates a doser relationship betweenAcalyphoideae, Crotonoideae, and Euphorbioideae, when compared with Phyllanthoideae and Oldfieldioideae. Previously Meeuse (1990) had arrived at the same condusion based on detailed research of seeds and seed coats. Moreover, serological studies by Jensen et al. (1994) confirmed that Phyllanthoideae are equally different fromAcalyphoideae, Crotonoideae, and Euphorbioideae. They suggest that the last three subgroups should be united in one phylogenetic unit. It may be conduded that wood anatomy supports a narrower concept of the fam­ ily Euphorbiaceae, restricting it to the three uniovulate subfamilies, as was recently proposed by Chase et al. (2002) based on molecular analyses.

ACKNOWLEDGEMENTS

Thanks are due to the Directors and Curators of the wood collections in Brunei Darussalam, Leiden (Lw), Madison (MADw), Reinbek (RHw), Tervuren (Tw), Wageningen (WlBw) for supplying wood sampies. I am indebted to D. Makhan for sections and macerations of the extensive material. The skilful handling ofthe photographs by H. Rypkema is gratefully acknowledged. Sincerest thanks are extended to my colleagues Jifke Koek-Noorman and Lubbert Westra for their continued interest. Lub­ bert Westra's painstaking reading of the original version of the text resulted in linguistic correction and suggestions for textual improvement. To Jifke Koek-Noorman I owe the greatest debt of gratitude. Without her daily support this paper would never have been accomplished. She devoted over a long period a great deal of her time to critical reading of the text, advising on the layout of the plates and converting my type-wrillen drafts into a digital file. Finally I wish to thank H.-I. Esser (München, Botanische Staatssammlung) for his comments on the final version of the manuscript.

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