IAWA Journal, Vol. 14 (4),1993: 373-389

WOOD STRUCTURE AND GENERIC STATUS OF SOME SOUTHERN AFRICAN CASSINOIDEAE ()

by

Robert H. Archer 1 and Abraham E. van Wyk H. G.W. J. Schweickerdt Herbarium, Department of Botany, University of Pretoria, Pretoria, 0002 Republic of South Africa

Summary Opinions differ on whether to treat Cas­ cies of Celastraceae with indehiscent fruits, sine in southern Africa in a wide sense, or to usually drupes or berries. recognise several segregate genera, such as On a world-wide basis, is some­ , Crocoxylon, Lauridia, Mys­ times treated in a very broad sense to include troxylon and Cassine s. str. A comparative Elaeodendron and a number of smaller genera anatomical study was made of mature wood comprising mainly southern African species representing 17 southern African species of with indehiscent and usually fleshy fruits Cassine s.l., Pleurostylia and the three mono­ (amongst others Kuntze 1891; Loesener 1892; typic genera, Allocassine, Hartogiella and Davison 1927; Hou 1962; Codd 1966). This Maurocenia (all members of the subfamily treatment of Cassine s.l. has received wide Cassinoideae). The wood structure is de­ support. However, the concept of an inclu­ scribed with emphasis on the taxonomic value sive Cassine s.l. could well be artificial as of quantitative and qualitative characters. authors, such as Loesener (1942; contrary to Various features were found to be diagnostic his 1892 treatment) and Robson (1965, 1966), at supraspecific level. The presence or ab­ subdivided the fleshy fruited southern Afri­ sence of scalariform perforation plates, sep­ can Celastraceae into a number of segregate tate fibres, various ray types, and additional genera, for example Allocassine, Cassine quantitative characters could be useful for s. str., Crocoxylon, Elaeodendron, Lauridia taxonomic application, especially for generic and Mystroxylon. It is suggested that multi­ delimitation. Three principal wood types, of disciplinary research may lead to an improved which one encompasses three subtypes, are understanding of the generic limits of not recognised among the species examined. only Cassine, but also the rest of the family. Wood anatomical evidence tells against a The wood structure of several species of wide generic concept for Cassine, and fa­ Celastraceae was described in varying detail vours the recognition of segregate genera. by authors such as Moll & Janssonius (1908), Key words: Systematic wood anatomy, taxon- Solereder (1908), Loesener (1892, 1894, omy, Cassine s.l., Cassinoideae, Celas­ 1942), Pearson & Brown (1932), Record traceae. (1938), Desch (1941, 1954), Record & Hess (1943), Metcalfe & Chalk (1950), Tortorelli Introduction (1956), Ingle & Dadswell (1961), Mennega This study forms part of a multidiscipli­ (1972), Kromhout (1975, 1977), Miles nary approach to a taxonomic revision of the (1978), Ilic (1987), Carlquist (1988a) and southern African members of the subfamily Zhang Xinying et al. (1990). Of these contri­ Cassinoideae (Archer 1990; Archer & Van butions, those of Record (1938) and Record Wyk 1992, 1993). Established by Loesener & Hess (1943) are the most elaborate and (1892), this subfamily accommodates the spe- contain wood anatomical descriptions for 16

1) Present address: National Botanical Institute, Private Bag XlOl, Pretoria, 0001 Republic of South Africa.

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celastraceous genera including Cassine s.l. lata (shrub or small tree) and C. tetragona Metcalfe and Chalk (1950) comprehensively (liana) were collected from stems, measuring summarised the older literature. More recent 30-80 mm in diameter, whereas the stem publications on the wood anatomy of Celas­ diameter in all the other taxa exceeded 100 traceae s. str. are scanty and fragmentary mm. Samples were fixed in FAA (Johansen (Gregory 1980). 1940). Wood of C. schlechteriana (under Except for the contributions by Kromhout which some workers have included C. stuhl­ (1975, 1977) and Dyer (1988), which con­ mannii) was not available for comparative tain information on wood of some celastra­ study. ceous species, and the summarised data in Standard procedures for wood anatomy Metcalfe & Chalk (1950), very little work were used to prepare transverse, radial and has been done on the comparative wood tangential sections, macerations and blocks structure of the southern African species of for SEM observations (Van Wyk et al. 1983). Cassine s.l. The lack of commercially impor­ Measurements of wood anatomical features tant timber species in the region may be one were made with a personal computer equip­ of the reasons for the paucity of comparative ped with a graphics tablet in combination wood anatomical studies on the group. with a projection LM. Means, standard devi­ For a better understanding of the ation, minimum and maximum values are of Cassine, extensive taxonomic evidence based on at least sixty individual measure­ from a variety of sources is required. In this ments. Septate libriform fibres were not clear­ study the taxonomic significance of wood ly discern able in macerations and have there­ anatomical characters of the southem African fore not been measured in these preparations. species of Cassine s.l. and the three mono­ Crude estimates of the length of the latter typic genera, Hartogiella, Maurocenia and elements were made on longitudinal sections. Allocassine, was studied. Our emphasis has Descriptive terminology follows Carlquist been mainly placed on those differentiating (1988b) and the recommendations of the In­ characters that might be employed taxonomi­ ternational Association of Wood Anatomists cally on the supraspecific level. Although also (IAWA Committee 1989). placed under the Cassinoideae by Loesener (1892, 1942), Pleurostylia, with its dry fruits, Results and Discussion is not considered to be closely related to the other southern African Cassinoideae. It has Anatomically three wood types are distin­ nevertheless been included in the present guishable and described below. Qualitative study for comparative purposes. and quantitative data are summarised in Tables 2 and 3. Alternative generic treatments of taxa Materials and Methods are mentioned in Table 1. Fifty-five samples of wood representing 17 southern African species of Allocassine, Wood type A (Figs. 1, 9, 15; Table 2) Cassine, Hartogiella, Maurocenia and Pleu­ Diagnostic characters: Vessel elements rostylia were studied using mainly light mi­ with scalariform perforation plates; septate li­ croscopy (LM), and to a lesser extent, scan­ briform fibres in apotracheal banded arrange­ ning electron microscopy (SEM). Species ment between fibre-tracheids; without axial names and their author citations are supplied parenchyma. in Table 1. Voucher specimens and slides are Material studied: Cassine crocea: Archer housed in the H.G.W.J. Schweickerdt Her­ 303, 366, Briers s. n. - C. matabelicum: barium (PRU) and are listed under Results. Venter & Archer 184, 185, Venter, Archer & Codes from Stem's Index Xylariorum (1988) Hahn 408. - C. papillosa: Archer 263, 283, indicate the sources of other samples. 325,344,446, PFPw X787, Van Greuning Wood samples were collected with an in­ 626. - C. transvaalensis: Archer 245, 246, crement borer from upright stems at about 325, Pienaar & Archer 1338. 1 m height. Samples of A. laurifolia (liana), Growth rings absent or weakly defined C. parvifolia (shrub or small tree), C. reticu- owing to the presence of slightly denser zones

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Table 1. Summary of different taxonomic treatments of southern African Cassinoideae, and a proposed new generic classification.

Species of southern African Cassinoideae; Alternative generic Wood Proposed new generic Cassine treated in a wide sense 1 treaunent2 type treaunent3

Cassine crocea (fhunb.) Kuntze Crocoxylon Eckl. & Zeyh. C. transwlfJlensis (Burtt Davy) Codd Crocoxylon Eckl. & Zeyb. A C. matabelicum (Loes.) Steedman Elaeodendron Jacq. f. C. papillosa (Hochst.) Kuntze 4 Elaeodendron Jacq. f.

C. barbara L.

C. parvifolia Sond. Cassine L. s. str. Cassine L. s. str. Bl C. peragua L.

Hartogiella schinoides (Spreng.) Codd Hartogiella Codd HartogieIIa?

Mauroceniafrangularia (L.) Mill. Maurocenia Mill. Maurocenia Mill.

Cassine tetragona (L. f.) Loes. Allocassine N.K.B. Robson B2 Lauridia Eckl. & Zeyh. C. reticulata (Eckl. & Zeyh.) Codd Lauridia Eckl. & Zeyh.

Allocassine laurifolia (Harv.) N.K.B. Robson Allocassine N.K.B. Robson B3 Allocassine N.K.B. Robson

Cassine aethiopica Thunb. Mystroxylon Eckl. & Zeyh. Mystroxylon Eckl. & Zeyh. sect. Eumystroxylon Loes. C. burkeana (Sond.) Kuntze

C. eucIeiformis (Eckl. & Zeyh.) Kuntze C Mystroxylon Eckl. & Zeyh. nov. A sect. Pseudoscytophyllum Loes. C. maritima (H. Bol.) L. Bol.

PleurastyUa capensis (furcz.) Loes. 5 Pleurastylia Wight & Am. Pleurostylia Wight & Am.

1) E.g., Davison 1927; Codd 1966, 1983; Gibbs Russell et aI. 1987; Arnold & De Wet 1993. 2) E.g., Loesener 1942; Robson 1965, 1966. 3) Archer 1990; Archer & Van Wyk 1992, 1993. 4) Incorrectly referred to as Cassine crocea, Elaeodendron croceum or Crocoxylon croceum by many authors. The identity of existing wood samples or slides carrying the epithet' croceum' should be considered suspect, and is most likely to be Cassine papillosa. 5) With its dry fruit, Pleuroslylia does not appear to be closely related to the other southern African Cassinoideae.

of fibres. Wood diffuse-porous, rarely ap­ Vessel elements with short to long tails, pearing semi-ring-porous. length (including tails) 488-749 (130-1250) Pores predominantly solitary or rarely in /lm. Perforation plates exclusively scalariform small radial multiples, numerous, (78-)104- and oblique with less than ten bars, but 10- 139(-188)/mm2, round to oval or slightly 18 in C. papillosa, bars sometimes branched. angular, tangential diameter 30-40 (11-61) Intervessel pits if present rounded to polygo­ 11m, walls 5-8 11m thick. nal, alternate, often coalescent, 4-8 /lm in

Downloaded from Brill.com10/04/2021 10:09:11AM via free access Table 2. Summary selected qualitative and quantitative wood anatomical data on Allocassine, Cassine s.l., Hartogiella, Maurocenia and Pleurostylia of I~ (+ = present; - = absent).

C 1>l ] C ~ OJ ~ j", c i3 .;;; .!l P. '"E Vessel elements Fibre-tracheid ~] ta-'S .c» -5 Material .c~ u 8- '" length "'" ~ '"~ c ~ ::a :z .~ c u = '-o 0 ~ Length Tangential pore ~.9 <0::"'" » » ,.:a;i ~ ... ~ diameter E·~ .!l '" u .::! » ~~ E.8 ~ 3 '" "» -g K "'" OJ X Range X Range Range ~8-~& ..:: a ~'" I'Q X Wood type A '" Cassine crocea + 10 + he-I 2-5 Procumbent 488 (190-950) 29.7 (13.3-52.3) 957 (330-2270) Cassine matabelicum + 8 + he-I 2-4 Procumbent 569 (244-903) 39.5 (15-47.1) 1028 (495-2069) Cassine papil/osa + 18 + he-I (HA) 2-4 Procumbent 749 (250-1250) 34.7 (10.8-46.1) 1340 (600-2450) Cassine transvaalensis + 10 + he-I (HA) 4-7 Procumbent 555 (130-970) 36.7 (13.1-61.4) 1048 (420-2200)

Wood type B Allocassine laurifolia + he-III 1 Upright 560 (330-1140) 39.4 (14.0-46.7) 835 (250-1150) Cassine barbara + he-I 3 Procumbent 490 (200-710) 24.9 (20.5-37.7) 690 (380-900) Cassine parvifolia + he-III 1 Square 630 (340-1080) 24.8 (17.7-36.8) 770 (370-1120) + he-I (HA) 2-4 Procumbent 556 (200-1010) 31.1 (15.9-53.0) 800 (280-1550) ...... Cassine reticulata + he-III Square 650 (370-900) 21.2 (13.1-32.5) 770 (490-1370) :>

Downloaded fromBrill.com10/04/2021 10:09:11AM Cassine tetragona + he-III 1 Square 570 (270-1000) 68.0 (42.4-80.8) 815 (440-1550) ~ Hartogiella schinoides he-I 2 Procumbent 640 (440-970) 31.9 (14.9-44.1) 813 (420-1330) ...... + 0 Maurocenia frangularia + he-III 1(-2) Square 495 (340-950) 29.4 (24.1-47.6) 640 (430-1150) ac ~ Wood type C <:: Cassine aethiopica + he-HA (I) 4-5 Procumbent 424 (150-740) 32.6 (18.1-46.9) 810 (400-1550) f2...... Cassine burkeana + he-HA 4-5 Procumbent 320 (140-630) 26.4 (15.7-37.7) 700 (300-1230) .... Cassine eucleiformis + he-IIA (I) 2-5 Procumbent 476 (180-900) 24.9 (14.4-37.3) 723 (270-1153) Cassine maritima + he-IIA (I) 4-5 Procumbent 480 (340-640) 25.5 (17.2-41.3) 655 (430-980) ~ ...... Pleurostylia capensis + he-HA 3-4 Procumbent 607 (473-936) 34.0 (22.1-37.5) 1002 (650-1614) \0 via freeaccess \0 w Archer & Van Wyk - Wood of southern African Cassinoideae (Celastraceae) 377 diameter. Vessel-ray pits similar to intervas­ Growth rings absent or weakly defined cular pitting but half-bordered or with reduced owing to the presence of slightly denser zones borders. Frequently with amorphous depos­ of fibres. Wood diffuse-porous, rarely ap­ its. Tyloses rarely present, thin-walled. pearing semi-ring- porous. Imperforate tracheary elements consist of Pores predominantly solitary or rarely in two types of cells: thick-walled fibre-tra­ small radial multiples, numerous, (65-)85- cheids with pits mostly conspicuously bor­ 158(-189)/mm2, round to oval or slightly dered, and thin-walled septate libriform fibres. angular, tangential diameter 21-68 (14-81) Fibre-tracheids 912-1340 (303-2450) Ilm Ilm (68 Ilm in C. tetragona), walls 4-8 Ilm long, pits conspicuous, 2-5 Ilm in diameter, thick. density on radial and tangential walls more or Vessel elements with short to long tails, less equal. Cell walls vary from thick to very length 490-650 (200-1140) Ilm. Perforation thick. Fibre-tracheid bands alternating with plates simple and oblique. Intervessel pits if 4-10 cells wide bands of thin-walled septate present rounded to polygonal, alternate, often libriform fibres closely resembling axial pa­ coalescent, 4-8 Ilm in diameter. Vessel-ray renchyma, with simple slit-like pits, shorter pits similar to intervascular pitting but half­ than fibre-tracheids. bordered or with reduced borders. Occasion­ Axial parenchyma rare or absent. ally with tanniniferous deposits. Rays uni- and multi seriate (heterogeneous Imperforate tracheary elements consist of type I), up to 8 cells wide, 3-60 cells high, two types of cells: thick -walled fibre-tracheids heterocellular with procumbent body ray cells, with pits mostly conspicuously bordered [in­ with 1-5 rows of upright marginal cells. Per­ conspicuous in the two lianes A. laurifolia forated ray cells very rarely noted. and C. tetragona (approaching ordinary libri­ Crystals of calcium oxalate always pris­ form fibres)], and thin-walled septate libri­ matic, common in ray cells. form fibres. Fibre-tracheids 640-835 (250- Additional features: Usually no visual dis­ 1550) Ilm long, pits conspicuous, 2-5 Ilm in tinction between heart- and sapwood. Colour diameter, density on radial and tangential walls of wood pale to dark brown. Froth test posi­ more or less equal. Cell walls vary from thick tive for species tested (Dyer 1988). to very thick. Septate libriform fibres present Note: Except for minor quantitative varia­ in concentric bands, 8-12 cells wide, shorter tion, it is not possible to distinguish between than fibre-tracheids. the wood structure of the species with this Axial parenchyma rare or absent. wood type (Table 2). Rays 1-3 cells wide, 4-50 cells high, bi­ seriate section not much thicker than uniseri­ Wood type B (Figs. 2-6, 10-13, 16-18; ate section, heterocellular with procumbent Table 2) body ray cells, heterogeneous type IIA, or Diagnostic characters: Vessel elements uniseriate and nearly homocellular (hetero­ with simple perforation plates; septate libri­ geneous III) with predominantly square (C. form fibres in apotracheal banded arrange­ reticulata and C. tetragona) or upright (A. ment between fibre tracheids or ordinary non­ laurifolia) cells. septate fibres; without axial parenchyma. Crystals of calcium oxalate prismatic, com­ Material studied: Cassine barbara: Van mon in ray cells. Wyk AIB8. - C. parvifolia: Van Greuning Additional features: Usually no visual dis­ 627. - C. peragua: Archer 238, 257, 285, tinction between heart- and sapwood. Colour PFPw X879, id. 1552, Van Jaarsveld 10581, of wood pale to dark brown. In one species 10583. - C. reticulata: Archer 311, Van der (C. tetragona) wedge-shaped radial invagina­ Walt s.n. - C. tetragona: Van Wyk 8276, tions of bark result in an irregular outline of AlOn. - Allocassine laurifolia: Van Wyk the wood cylinder. Froth test positive for 8307, 8397. - Hartogiella schinoides: Archer species tested (Dyer 1988). 285, Van Jaarsveld 10580, 10582. - Mauro­ Note: This is a fairly heterogeneous group ceniafrangularia: Van Wyk A1066, Zeyher which varies mainly in ray structure. Wood 69 (Uw 20500). type B can be subdivided into three SUbtypes:

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Table 3. Summary of selected wood anatomical features of some extra-southern African species of Cassine s.l. (including Elaeodendron) (+ = present; - = absent).

Taxa Scalarifonn Septate Axial Source perforation fibres parenchyma plates

Cassine australis (Vent.) Kuntze + + Hic 1987 C. buchananii Loes. + + Loesener 1894 C. curtipetala (EmU.) Kuntze + + C. glauca (pers.) Kuntze + + Banded Moll & Janssonius 1908 C. orientalis (Jacq. f.) Kuntze (Venter et aI. 3621 ) + + C. orientalis (U 184721) ± Diffuse C. quadrangulata (Reiss.) Kuntze + C. stuhlmannii (Loes.) Blakelock + + Loesener 1894, Barefoot & Hankins 1982 C. xylocarpa Vent.2 + + Record 1934, Record & Hess 1943 Elaeodendron aJzelii LoeS.2 + Loesener 1894

1) The identity of one of these samples is, although celastraceous, likely to be wrong. 2) Infonnation from the literature only.

Subtype Bl (Figs. 2-4, 10, 11, 16): body rangement between fibre-tracheids; without ray cells procumbent with 2-4 rows of mar­ septate fibres. ginal upright cells (C. barbara, C. peragua and Material examined: C. aethiopica: Archer H. schinoides), rays uniseriate with upright 244,247,286,327,379, Schlieben 1515, E. to procumbent cells in C. parvifolia. Except Africa (Uw 15495). - C. burkeana: Archer for C. parvifolia, the wood of these species 210,211. - C. eucleiformis: Archer 299,233, is very similar. 235, 240, 241, 242, Van Wyk A1048. - C. maritima: Archer 277, Van Greuning 628. - Subtype B2 (Figs. 5, 6, 12, 17): ray cells Pleurostylia capensis: Venter 13624, PFPw predominantly square (C. reticulata), occa­ X119. sionally with marginal cells slightly upright Growth rings absent or weakly defined (C. tetragona and M.jrangularia). The large owing to the presence of slightly denser zones average pore diameter and deeply penetrating, of fibres. Wood diffuse-porous, rarely ap­ wedge-shaped, radial secondary phloem in­ pearing semi-ring-porous. clusions encountered in C. tetragona (a liane Pores predominantly solitary or rarely in or scrambling shrub) are very characteristic. small radial multiples, numerous, (73-)96- 120(-136)/mm2, round to oval or slightly Subtype B3 (Figs. 13, 18): all ray cells con­ angular, tangential diameter 25-34 (14-47) spicuously upright (A. laurifolia). 11m, walls 4-8 11m thick. Vessel elements with short to long tails, Wood type C (Figs. 7, 8, 14; Table 2) length (including tails) 320-607 (140-936) Diagnostic characters: Vessel elements 11m (607 11m in P. capensis). Perforation plates with simple perforation plates; axial paren­ simple and oblique. Intervessel pits if present chyma abundant, in apotracheal banded ar- rounded to polygonal, alternate, often coales-

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cent, 4-8 Ilm in diameter. Vessel-ray pits Discussion of selected wood anatomical similar to intervascular pitting but half border­ features ed or with reduced borders. Occasionally with tanniniferous deposits. Growth rings and vessels Imperforate tracheary elements consist of Growth rings are usually faint, but can be fibre-tracheids with pits mostly conspicu­ distinguished by slightly denser fibre-tra­ ously bordered, 655-1002 (270-1614) Ilm cheids in the late wood. Wood is diffuse-por­ (1002 Ilm in P. capensis) long, pits conspic­ ous, although pores may be wider or more uous, 2-5 Ilm in diameter, density on radial numerous in the early wood, thus giving the and tangential walls more or less equal. Cell impression of being semi-ring-porous. Ves­ walls vary from thick to very thick. sels filled with thin-walled tyloses and/or Axial parenchyma apotracheal, widely amorphous material have been observed often banded. Bands 4-12 cells wide, up to 5 bands in samples but have little if any taxonomic per growth ring. significance. The length and tangential diam­ Rays 1-8 cells wide, 5-60 cells high, eters of vessel elements are given in Table l. heterocellular with procumbent body ray cells, Vessel-element length weakly correlates with heterogeneous type ITA, uniseriate rays short the three wood types distinguished in this with mostly upright cells, multiseriate rays study, and can be used to assist in their sepa­ with a multi seriate portion of procumbent ration. cells and usually with a short uniseriate mar­ Dimensional variation and structure of gin. vessel elements in wood of southern African Crystals of calcium oxalate prismatic, oc­ species of Cassine agree with available data casionally in axial parenchyma, common in on other Celastraceae of southern Africa ray cells. (Kromhout 1975, 1977; unpublished results) Additional features: Usually no visual dis­ and the rest of the world (Moll & Jansso­ tinction between heart- and sapwood. Colour nius 1908; Record 1938; Ingle & Dadswell of wood pale to dark brown. Froth test posi­ 1961). tive for species tested (Dyer 1988). Perforation plates with 4 to 18 bars were Note: This wood type forms a very homo­ found in only four species of wood type A. geneous group with little interspecific varia­ In this study, as well as in the literature tion. Pleurostylia capensis, however, can be (Loesener 1894), the wood of C. stuhlmannii, recognised by its much longer vessel ele­ which Robson (1966) considered synony­ ments and fibre-tracheids. mous with C. schlechteriana, has also been observed with scalariform perforation plates. Wood of extra-southern African species of The work of Frost (1930) amongst others, Cassine s.l. has shown the type of perforation plate to be Material studied: Cassine australis: Aus­ a good taxonomic character not easily modi­ tralia, Uw 18469. - C. buchananii: Mennega fied by environmental variation. The wood of & Baretta 224, Kenya, Uw 18917. - C. cur­ American and Javanese species of Elaeoden­ tipetala: New Caledonia, Uw 18470. - C. dron is characterised by the presence of ves­ glauca: Jayawardana 52, Ceylon, Uw 18503. sels with scahuiform perforation plates (Moll - C. orientalis: Director of forests, Mauritius & Janssonius 1908; Record 1938). The lack (Uw 18472), Lorenze 2547 (MAU), twig­ of scalariform perforation plates has been wood, Venter, Archer & Hahn 326, Zimbab­ considered characteristic of all other celastra­ we, planted as ornamental trees. - C. quadran­ ceous genera with indehiscent fruit (Loesener gulata: Archer & Van Wyk s.n., cult. Dur­ 1892, 1942; Record 1938; Record & Hess ban Botanic Garden (NH). - C. stuhlmannii: 1943). Scalariform perforations have been Schlieben 540, E. Africa, Uw 15631. used by workers such as Loesener (1942), Selected wood anatomical features of these Hartog-Van Ter Tholen & Baas (1978) and taxa are summarised in Table 3. Also included Mennega (pers. comm.) to justify Elaeoden­ in Table 3 is published data on Cassine xylo­ dron as a taxon distinct from Cassine and carpa and Elaeodendron afzelii. Mystroxylon.

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~~ ' - 1 ~ ,,~ ~ ~ ~. ~ lIIIjoiO~E= ~ ~ ~ Ii'" 11,,... i b1

M ~ ~ .. tq Be

IJIfiI 1M "l t.i ~ lC \F.. ~ ~~ ~ £. ~,.;~ ~ 2'.A b ~ ~ .}(W(IW

Figs. 1-4. TS - 1: Cassine papillosa (Van Greuning 626), wood diffuse-porous with bands of thin-walled septate fibres. - 2: C. parvifolia (Van Greuning 627) & 3: C. peragua (Archer 257), wood diffuse-porous with weakly defined ring boundary. - 4: Hartogiella schinoides (Van Jaars­ veld 10580), wood diffuse-porous with bands of thin-walled septate fibres. - Scale bars: 100 JlIll.

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Figs. 5-8. TS - 5: Mauroceniafrangularia (Van Wyk A1066), wood diffuse-porous. - 6: Cas­ sine tetragona (Van Wyk A1071), with wide vessels. -7: C. eucleiformis (Archer 240), wood diffuse-porous with bands of axial parenchyma. - 8: C. aethiopica (Archer 244), wood diffuse­ porous with bands of axial parenchyma. - Scale bar = 100 ~m.

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III I 13 J l1 ,. ~J

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In the literature, the following non-south­ According to Zhang Xinying et al. (1990) ern African species of Cassine s.l. (= Elaeo­ large vessel-ray pits occur in only a few dendron) are described as characteristically celastratraceous genera, namely Bhesa, Elaeo­ possessing scalariform perforation plates: E. dendron, Denhamia and Perrottetia. How­ aJzelii (Loesener 1894); C. glauca with 1-4 ever, no supra specific differences were ob­ bars (Moll & Janssonius 1908) or with sim­ served in vessel pit dimensions of Cassine and ple and scalariform plates mixed (Solereder Elaeodendron. Large vessel-ray pits were not 1908); and C.xylocarpa (Record 1938; Record observed, except in one sample of C. stuhl­ & Hess 1943). The only other celastraceous mannii. taxa known to have scalariform perforation Under SEM very weakly defined vestures plates are Goupia (Record 1938; Record & were seen in the vessel-fibre pits of C. papil­ Hess 1943), Bhesa (previously named Kurri­ losa. The structure and taxonomic value of mia) (Solereder 1908; Zhang Xinying et al. these vestures require further study. 1990), Perrottetia (Versteegh 1968; DeBuhr 1978), and Empleuridium with both simple and scalariform plates (Goldblatt et al. 1985). Imperforate tracheary elements Some of these genera were often placed in a Vasicentric tracheids have not yet been family of their own (Goupia) or accommodated recorded in Cassine s.l. Although they have in other families (Empleuridium in Rutaceae). been reported to be common in the Hippocra­ Scalariform perforation plates are therefore teoideae (Metcalfe & Chalk 1950; Mennega rarely encountered in the core Celastraceae. 1972), they appear to be absent in southern Although exceptions exist (Table 3), the African members of this subfamily (unpub­ presence of scalariform perforation plates is lished data). considered an important taxonomic feature of Carlquist (1988a) described the imperfo­ wood type A, thus supporting the recognition rate tracheary elements of Catha, Elaeoden­ of the segregates Crocoxylon and Elaeoden­ dron, Celastrus and May tenus as septate libri­ dron. form fibres, septate fibre-tracheids and tra­ In the past, considerable confusion existed cheids as well as vasicentric tracheids. We regarding the taxonomic usefulness of scala­ prefer to use the term fibre-tracheids rather riform perforation plates in Cassine s.l. The than tracheids in this study. The fibres usu­ inconsistent application of names of both ally have bordered pits, 2-5 Ilm in diameter. Elaeodendron and Cassine to southern Afri­ These are apparently not conductive and are can species, e. g. in Metcalfe & Chalk (1950) distinctive in most taxa. Pits are frequent on and Blakelock (1956), led to the misconcep­ both radial and tangential walls. This corre­ tion that the presence of scalariform perfora­ sponds with most definitions of fibre-tra­ tion plates could not be used as a taxonomic cheids (Metcalfe & Chalk 1983; Carlquist criterion. Up to now only a small number of 1988b; IAWA Committee 1989). species of Elaeodendron have been examined Fibre-tracheid length (Table 2) is fairly (Loesener 1894, 1942; Moll & Janssonius constant for a species or wood type, and 1908; Record 1938). More wood anatomical could be useful for the differentiation of spe­ studies on extra-southern African species of cies or genera. Although we only measured Cassine s.l. are required to establish the con­ the length of a few septate fibres, these tend sistency and usefulness of scalariform perfo­ to be shorter than the fibre-tracheids. ration plates as a taxonomic character.

Figs. 9-14. TLS - 9: Cassine transvaalensis (Archer 245), rays multiseriate. - 10: Hartogiella schinoides (Van Jaarsveld 10580), rays 1- or 2-seriate. -11: Cassine peragua (Archer 257), rays 2- or 3-seriate. - 12: C. reticulata (Van der Walt s.n.), rays uniseriate. - 13: Allocassine laurifolia (Van Wyk A1073), rays uniseriate with all cells conspicuously upright. - 14: Cassine aethiopica (Archer 244), rays multiseriate, fibres left and axial parenchyma right. - Scale bar = 100 Ilm.

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Figs. 15-18. RLS - 15: Cassine crocea (Archer 366), rays heterogeneous, note scalariforrn per­ foration plates. - 16: Hartogiella schinoides (Van Jaarsveld 10580), thin-walled septate fibres.- 17: C. reticulata (Van der Walt s.n.), ray with predominantly square cells. -18: Allocassine laurifolia (Van Wyk A1073), ray with upright cells. - Scale bar = 100 Jlm.

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Multiseriate bands of thin-walled septate An intermediate condition of bands com­ libriform fibres, 3-12 cells wide, occur posed of both septate fibres and axial paren­ among the fibre-tracheids in most of the spe­ chyma was reponed in C. glauca and other cies. These bands are comparable in distri­ Indian species of Cassine s.l. (Moll & Jans­ bution and appearance to the bands of axial sonius 1908; Ghosh & Purkayastha 1960). parenchyma in C. aethiopica, C. burkeana, Our study confirms these observations. No C. eucleiformis, C. maritima and Pleuro­ such intermediate state was noted in the south­ stylia. Broad bands of either parenchyma or ern African species of Cassine. Although septate fibres are characteristic of Cassine, there is a possibility that septate fibres could Celastrus p.p., Elaeodendron p.p., Fraun­ grade into axial parenchyma, this was not ob­ hojera, May tenus p.p. (spiny members = served by us. The distinction between septa Gymnosporia), Hartogielia, Maurocenia and and cell walls separating a strand of cells pro­ Plenckia (Metcalfe & Chalk 1950). Metcalfe vides a reliable indicator of the two types of and Chalk (1950) added that "these bands of cells. The presence of either parenchyma or septate fibres are exactly comparable in distri­ septate fibres is therefore an extremely use­ bution with the multi seriate bands of paren­ ful character for the delimitation of southern chyma occurring in other species, and in a African celastraceous taxa. A similar distinc­ single genus the bands may be composed of tion between septate fibres in some species septate fibres in one species and of paren­ and parenchyma in another was also noticed chyma in another." This type of fibre dimor­ amongst southern African species of May­ phism has been described in many other tenus s.l. (unpublished data). The possible groups, including Melastomataceae (fer Welle direction of phylogenetic specialisation in this & Koek-Noorman 1978) and Lythraceae morphological series is, however, not clear at (Baas & Zweypfenning 1979). A possible this stage. close functional relationship between axial parenchyma cells and thin-walled septate Axial parenchyma fibres has been suggested (Carlquist 1975, Wide bands, 3-8 cells wide, of apotracheal 1988b; Ter Welle & Koek-Noorman 1978). axial parenchyma are present in five of the Spackman & Swamy (1949), following a species (wood type C) (Fig. 20). Tanninifer­ survey of 6250 species, concluded that sep­ ous and, less frequently, crystalliferous axial tate fibres commonly occur in apotracheal parenchyma cells are present in C. aethiopica. and paratracheal patterns corresponding to However, no constant interspecific differ­ those of axial parenchyma. They also noted ences were noticed in wood type C. Axial that the proportion of septate fibres increases, parenchyma is rare or absent in wood of the with a corresponding decrease in axial paren­ remaining southern African species of Cas­ chyma. A theory of tracheid dimorphism has sine. In these species, the bands consist of been suggested by Carlquist (1988a), follow­ septate fibres which probably have the same ing a study involving taxa of six families, in­ function as axial parenchyma. cluding Celastraceae, where tracheids (fibre­ Except in C. glauca, axial parenchyma was tracheids in present study) occur in combi­ rarely encountered in wood of foreign spe­ nation with living, thin-walled, often septate cies of Cassine. Barefoot and Hankins (1982) fibre-tracheids or libriform fibres. illustrated axial parenchyma with gum con­ Mennega (1972) found that the presence tent in C. stulhmannii [Robson (1966) con­ of bands of septate fibres corresponded with sidered this species synonymous with C. the hippocrateaceous species with drupace­ schlechteriana]. However, we are convinced ous fruits. In the species with capsular fruit, that it is ray parenchyma cells that have been the septate fibres are inconspicuous. These illustrated, not axial parenchyma. groups are in accordance with Halle's (1962) The presence of banded axial parenchyma division of the African Hippocrateaceae into is considered to be taxonomically important, two subfamilies, namely the Hippocrateoi­ and is present in those species comprising the deae and Salacioideae [this distinction has also segregate genera Mystroxylon and Genus A. been suggested by Robson (1965)]. Genus A is provisional and is characterised

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by a different (from all other Cassine s.l.) togiella, Pleurostylia and Maurocenia. Soli­ floral morphology, glabrous leaves, elastic tary crystals occur exclusively in the axial and threads (trans-l,4-polyisoprene), interme­ ray parenchyma cells. The occurrence of diate stomatal type and a diagnostic bark crystalliferous cells varies considerably be­ type, amongst other characters (Archer 1990; tween samples, and no constant interspecific Archer & Van Wyk 1992, 1993). differences were found. Similar crystals have also been recorded in other species of Cassine Rays and many other genera of the Celastraceae Rays in wood type A, part of B, and C (Moll & Janssonius 1908; Metcalfe & Chalk are either heterogeneous and multiseriate with 1950), except in Bhesa, where they occur in procumbent cells distinct from the marginal chambered crystalliferous parenchyma cells upright cells, or uniseriate and then usually (Zhang Xinying et al. 1990). composed of predominantly upright cells. Colour of water and ethanol extracts, the The remaining taxa with wood type B have burning splinter test as well as the froth test uniseriate rays composed of either predomi­ proved to be of no taxonomic value. Dyer nantly square [C. reticulata, C. tetragona and (1988) reported a positive froth test in many M.frangularia (Figs. 16-19)], the latter with samples of Cassine. Hitherto no heartwood often biseriate rays present, or predominant­ fluorescence has been reported in members of ly upright cells (A. laurifolia; related to liane the Celastraceae (Dyer 1988; Avella et al. habit?) (Figs. 12 & 13). 1989; IAWA Committee 1989), except in There is a slight correlation between the ray Goupia, often referred to a family of its own types and the proposed wood types. Wood (Metcalfe & Chalk 1950). type A always displays Kribs heterogeneous I, whereas ray types II to III are confined to Taxonomic conclusions the remaining two wood types. The presence or absence of scalariform Compared to the axial parenchyma, amor­ perforation plates and the occurrence of bands phous deposits and crystals are more frequent­ of either axial parenchyma or septate fibres ly present in the ray cells. No constant inter­ are probably the most important wood char­ specific differences in the occurrence of tan­ acters to facilitate the subdivision of Cassine niniferous and crystalliferous cells were s.l. into more natural groups. Other useful noticed. characters are the ray type and, to a lesser Enlarged ray cells with perforations resem­ degree, the length of the vessel elements and bling the simple perforation plates of vessels fibres .. Three distinctive wood types, one have occasionally been observed in wood of with three SUbtypes, can be recognised from species of Cassine, Pleurostylia and of May­ the wood of the 17 southern African species tenus (unpublished results). These cells are examined. difficult to detect as only a very limited num­ The presence of scalariform perforation ber are present on a wood slide. Perforated plates in the wood of Elaeodendron was used ray cells have been reported in wood of vari­ by Loesener (1942) to distinguish between ous Celastraceae, including C. papillosa, C. Elaeodendron and Cassine. In our study a crocea, and C. australis (Chalk & Chattaway similar conclusion has been reached regard­ 1933). Although they are more frequently ing the taxonomic usefulness of the presence observed in species of wood type A, they do of scalariform perforation plates in southern not seem to be of any tax<;>nomic value. In African taxa of Cassine s.l. (wood type A). recent years perforated ray cells have been re­ Although the presence of scalariform perfo­ ported in many families, suggesting that they ration plates is not always consistent in wood are widespread (Carlquist 1989b). of those foreign species of Elaeodendron in­ vestigated (possibly the generic identity of Miscellaneous features these taxa is questionable), it seems to be a Prismatic crystals of calcium oxalate are stable taxonomic character segregating Croc­ frequently present in wood of all the investi­ oxylon and Elaeodendron from Cassine. Crit­ gated species of Allocassine, Cassine, Har- ical wood anatomical studies of most of the

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species of Cassine s.1. from as many parts Allocassine, Lauridia, Maurocenia and Pleu­ of its range as possible are needed to extend rostylia. There is also other evidence that fa­ current knowledge, and to evaluate the gen­ cilitates the delimitation of these taxa (Archer eral importance of this character. The wood 1990). Further wood anatomy studies on of southern African species of Crocoxylon more species of Cassine s.l. from outside and Elaeodendron is very similar. southern Africa are extremely desirable in fu­ The species included in wood type C can be ture taxonomic studies of Cassine as a whole. recognised by the presence of bands of axial parenchyma, and correspond with Mystroxy­ Acknowledgements lon, Pleurostylia and the proposed Genus A. We are grateful to Dr. 1. V. van Greuning, No significant differences in wood anatomy Mr. E. van Jaarsveld and Mr. N. van der Wait were found between Mystroxylon and Genus for collecting wood samples; to Dr. A.M.W. A. However, fibre-tracheids and vessel ele­ Mennega (Utrecht) and Mrs. S. Dyer (For­ ments tend to be longer in Pleurostylia ca­ estek, C. S. I. R.) for providing wood sam­ pensis. ples and slides; and to Miss G.L. Day for her The wood of the remaining species con­ critical reading and improvement of the forms to wood type B. This wood type is manuscript. This study was supported in part characterised by the presence of simple per­ by research grants from the Foundation for foration plates and septate fibres. Species of Research Development and the University of Cas sine s. str. can be separated from the re­ Pretoria. maining taxa of type B by the presence of Kribs' type II rays as opposed to type III References rays. The similarity of the wood of C. bar­ Archer, R.H. 1990. The taxonomic status of bara, C. peragua and Hartogiella support the Cassine L. s. I. (Celastraceae) in southern inclusion of H. schinoides in Cassine s. str. Africa. M.Sc. Thesis, Univ. of Pretoria. The uniseriate rays of C. parvifolia, compar­ Archer, R.H. & A.E. van Wyk. 1992. Paly­ ed to the multi seriate rays of Cassine s. str. nology and intergeneric relationships in can perhaps be explained by the small stem some southern African species of subfam­ diameter of the sample used. il y Cassinoideae (Celastraceae). Grana 31 : Robson (1965) has described Allocassine 241-252. with two species: A. lauri/olia and A. tetra­ Archer, R.H. & A.E. van Wyk. 1993. Bark gona. Codd's (1966) decision to retain only structure and intergeneric relationships in one species, A. laurifolia, within Allocassine, some southern African Cassinoideae (Ce­ seems to be justified in light of its prominent, lastraceae). IAWA Journa114: 35-53. predominantly upright ray cells only encoun­ Arnold, T.H. & B.C. de Wet. 1993. tered in this species. The wood of C. tetra­ of southern Africa: names and distribu­ gona and C. reticulata is very similar, being tion. Mem. Bot. Surv. S. Afr. 62: 1-825. characterised by square ray cells, supporting Avella, T., R. Deschamps & M. Bastin. 1989. the placement of these species in the genus Fluorescence study of 10,610 woody spe­ Lauridia. Considering observations of wood cies from the Tervuren (Tw) collection, anatomy, Allocassine and Lauridia seem to Belgium. IAWA Bull. n. s. 9: 346-352. be distinct from Cassine S.str. The wood of Baas, P. & R.C.V.J. Zweypfenning. 1978. Maurocenia is very similar to that of Lauri­ Wood anatomy of the Lythraceae. Acta dia, and the two genera are probably closely Bot. Neerl. 28: 117-155. related. Barefoot, A.C. & F.W. Hankins 1982. Iden­ Wood anatomy of the investigated species, tification of Modern and Tertiary woods. together with information from other sources Clarendon Press, London. (Archer 1990; Archer & Van Wyk 1992, Blakelock, R.A. 1956. Notes on African Ce­ 1993), provides strong support for the recog­ lastraceae, II. Kew Bull. 1956: 555-557. nition of a number of genera as proposed by Carlquist, S. 1975. Ecological strategies of Loesener (1942) and Robson (1965, 1966): xylem evolution. Univ. of California Cassine s. str., Mystroxylon, Elaeodendron, Press, Berkeley.

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Carlquist, S. 1988a. Tracheid dimorphism: A Hou, Ding. 1962. Celastraceae I, II. In: new pathway in evolution of imperforate Flora Malesiana, Series I, Vol. 6: 227- tracheary elements. Aliso 12: 103-118. 421. Carlquist, S. 1988b. Comparative wood anat­ IAWA Committee. 1989. IAWA List of omy. Springer-Verlag, Berlin. microscopic features for hardwood iden­ Chalk, L. & M. M. Chattaway. 1933. Perforat­ tification. IAWA Bull. n.s. 10: 219- ed ray cells. Proc. R. Soc. B 113: 82-92. 332. Codd, L.E. 1966. Celastraceae. The Cassine Hic, J. 1987. The CSIRO family key for hard­ complex. In: New and interesting records wood identification. CSIRO Australia, of African flowering plants. Bothalia 9: Division of Wood Technology, Technical 123-151. Paper No.8, Australia. Davison, J.D. 1927. Celastraceae. Bothalia Ingle, H.D. & H.E. Dadswell. 1961. The 2: 289-346. anatomy of the secondary xylem of south­ DeBuhr, L.E. 1978. Wood anatomy of For­ west Pacific tree species as an aid to their sellesia (Glossopetalon) and Crossosoma taxonomy. Tenth Pacific Science Con­ (, Rosales). Aliso 9: gress. Div. of Forest Products, CSIRO, 179-184. Australia. Desch, H.E. 1941. Manual of Malayan tim­ Johansen, D.E. 1940. microtechnique. bers I. Malay. For. Rec. 15: 1-328. McGraw-Hill Book Co. Inc., New York. Desch, H.E. 1954. Manual of Malayan tim­ Krornhout, C.P. 1975. 'n Sleutel vir die mi­ bers II. Malay. For. Rec. 15: 327-762. kroskopiese uitkenning van die vernaam­ Dyer, S.T. 1988. Wood fluorescence of in­ ste inheemse houtsoorte van Suid-Afrika. digenous South African trees. lAWA Bull. Bull. 50, Dept. of Forestry, Pretoria. n. s. 9: 75-87. Kromhout, C.P. 1977. 'n Studie van die Frost, F.H. 1930. Specialization in secon­ houtanatomie van die vernaamste inheemse dary xylem of dicotyledons. II. Evolution houtsoorte van Suid-Afrika en 'n sleutel of end wall of vessel segment. Bot. Gaz. vir hul mikroskopiese uitkenning. Ph.D. 90: 198-212. thesis, University of Stellenbosch, Stellen­ Ghosh, S.S. & S.K. Purkayastha. 1960. bosch. Characteristic arrangement of septate Kuntze, 0.1891. Revisio generum plantarum fibres in the wood of Averrhoa sp. Sci. secundum leges nomenclaturae internatio­ Cult. 25: 690-691. nales. Pars 1. Arthur Felix, Leipzig. Gibbs Russell, G.E., W.G. WeIman, E. Loesener, T. 1892. Celastraceae. In: A. Eng­ Retief, K.L. Immelman, G. Germishui­ ler & K. Prantl (eds.), Die natiirlichen zen, B.J. Pienaar, M. van Wyk & A. Pflanzenfamilien Ed. 1, 3, 5: 189-222. Nicholas. List of species of southern W. Engelmann, Leipzig. African plants. Ed. 2, Part 2. Mem. Bot. Loesener, T. 1894. Celastraceae africanae. Surv. S. Afr. 56: 1-270. III. Bot. Jahrb. 28: 150-161. Goldblatt, P., H. Tobe, S. Carlquist & V.C. Loesener, T. 1942. Celastraceae. In: A. Eng­ Patel. 1985. Familial position of the Cape ler/H. Harms & J. Mattfeld (eds.), Die genus Empleuridium. Ann. Missouri Bot. natiirlichen Pflanzenfamilien Ed. 2, 20b: Gard. 72: 167-183. 87-197. Duncker & Humblot, Berlin. Gregory, M. 1980. Wood identification: an Mennega, A. M. W. 1972. A survey of the annotated bibliography. IAWA Bull. n. s. wood anatomy of the new world Hippo­ 1: 3-41. crateaceae. In: A.K.M. Ghouse & M. Halle, N. 1962. Monographie des Hippocra­ Yunus (eds.), Research trends in plant teacees d' Afrique occidentale. Mem. Inst. anatomy. K.A. Chowdhury Commemo­ Fr. Afr. Noire 64: 1-245. rative Volume: 61-72. Tata McGraw-Hill, Hartog-Van Ter Tholen, R.M. den & P. Bombay, New Delhi. Baas. 1978. Epidermal characters of the Metcalfe, C.R. & L. Chalk. 1950. Anatomy Celastraceae sensu lato. Acta Bot. Neerl. of the Dicotyledons. Vols. 1 & 2. Claren­ 27: 355-388. don Press, Oxford.

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