IAWA Journal, Vol. 14 (1), 1993: 35-53

BARK STRUCTURE AND INTERGENERIC RELATIONSIllPS 01<' SOME SOUTHERN AFRICAN CASSINOIDEAE (CELASTRACEAE)

by

Robert H. Archer1 andAbraham E. van Wyk H.G.W.J. Schweickerdt Herbarium, Department of Botany, University of Pretoria, Pretoria, 0002 Republic of South Africa

Summary At present Cassine in southern Africa Wyk 1992). Established by Loesener (1892), is treated in a wide sense (s.I.), including this subfamily accommodates those species amongst others Allocassine p. p., Cassine of Celastraceae with indehiscent fruits, usu­ s. str., Crocoxylon, Elaeodendron, Lauridia, ally drupes or berries. and Mystroxylon. A comparative anatomical There is considerable diversity of opinion study was made of mature bark representing regarding the delimitation and recognition of 16 southern African species of Cassine s.l., genera among the species of Cassine s.1. and the monotypic Allocassine, Hartogiella Various authors (Loesener 1894, 1942; Rob­ and Maurocenia (all members of the subfam­ son 1965, 1966) advocate smaller, more ho­ ily Cassinoideae). Six bark types are distin­ mogeneous genera, while Davison (1927), guished on the basis of the type of scleren­ Hou (1962), Codd (1966), Kostermans chymatous elements in the secondary phloem; (1986) and current herbarium practice at the presence or absence of styloid crystals, e1as­ National Herbarium, Pretoria (PRE) (Gibbs tic threads, and sclerified phelloderm; strati­ Russell et al. 1987), prefer to treat Cassine in fied homogeneous phellem; and degree of a wide sense, so as to include Allocassine rhytidome development. These correlate to a p.p., viz. A. tetragona, Crocoxylon, Elaeo­ considerable extent with the generic subdivi­ dendron, Lauridia, and Mystroxylon. For the sion of Cassine s.l. proposed by Loesener last two decades the treatment of Cassine in (1942) and Robson (1965). On the basis of a broad sense has received strong support bark anatomy and other evidence, it is pro­ worldwide (e.g. Dyer 1975; Mabberley 1987; posed that the circumscription of Cassine be Jessup 1984). The accumulation of new evi­ restricted to include only the southern African dence from morphology and anatomy, as species C. peragua and C. parvifolia, and pos­ weH as other sources, might accomplish a sibly Hartogiella. Crocoxylon, Elaeodendron, better understanding of generic limits in the Lauridia and Mystroxylon should be reinstat­ Celastraceae. ed or maintained, although with some modifi­ Comparative bark anatomical studies on cation of the originally defined generic limits. members of the Celastraceae are scanty. Roth (1973, 1981) describes the bark anatomy of Key words: systematic bark anatomy, taxon- woody neotropical species of Celastraceae. omy, Cassine s.l., Cassinoideae, Celas­ Zahur (1959), in a comprehensive survey of traceae. secondary phloem structure in dicotyledons, studied a few species of Celastraceae, but the Introduction anatomical description of this family was ap­ This study forms part of a multidiscipli­ parently accidentally omitted from this publi­ nary approach towards a taxonomic revision cation. Observations on celastraceous bark of the southern African members of subfam­ structure have also been provided by Weber ily Cassinoideae (Archer 1990; Archer & Van (1913), Thorenaar (1926) and Chung & Park

1) Present address: National Botanical Institute, Private Bag X101, Pretoria, 0001 Republic of South Africa.

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(1975). However, no information on the ana­ Bark sampIes were removed at approxi­ tomieal structure of the bark of Cassine could mately 0.5 m height from vertical boles not be found in the literature. less than 100 mm in diameter, and fixed in As an aid towards the classification of FAA (Johansen 1940). Standr.rd procedures woody taxa, the potential taxonomie signifi­ for wood anatomy were used to prepare trans­ cance of bark anatomy has been neglected. verse, radial and tangential seetions, 15-20 The bark anatomy of celastraceous species 11m thiek, from unembedded bark sampIes on hitherto investigated by us, suggests that bark a Reichert sliding rnicrotome. These were sup­ structure could contribute considerably to­ plemented by hand-cut sections. wards the delimitation of taxa, particularly at Sections were double stained in safranin 0 the generic level. In southern African Celastra­ and fast-green FCF (Johansen 1940), and ceae, bark structure is often more useful for mounted permanently in enteIlan (Art. 7961, diagnostic purposes than is wood structure E. Merck, Darmstadt). The phloroglucinol/ (Archer 1990 & unpublished results). hydrochloric acid test and Sudan black B Because of their ethnobotanical impor­ were used for detecting lignin and suberin re­ tance, there is a demand for bark anatomical spectively (Jensen 1962). information on African trees. This would fa­ Hand-cut seetions of the non-collapsed cilitate the identification of bark fragments secondary phloem, mounted in resorcin blue which are extensively traded by tradition al (O'Brien & McCully 1981) or aniline blue healers. Many trees with sought-after barks (Eschrich & Currier 1964), were viewed using are vulnerable to overexploitation. A database bright-field and fluorescence optics to exam­ for the identification of barks is needed, not ine sieve plates. Macerates of a few sampies only for the proteetion of tree species, but were prepared with Schulze's solution (Mc­ also to exert control over the identity of barks Lean & Ivimey-Cook 1941). sold or administered to the public. Barks of Drawings were made using a camera luci­ several species of Cassine s.l. are extensively da. Observations of the rhytidome pose a used in traditional medicine, especiaIly those problem because its brittleness causes it to be containing conspieuous orange pigments. easily tom apart and lost during sectioning. In this paper the comparative bark anat­ To study this tissue, clean-cut pieces of bark omy of the southern Afriean members of the were exarnined under a dissecting rnicroscope Cassinoideae, comprising Cassine s.l. and (Van Wyk 1985). Histochemical testing for the three monotypie genera, Allocassine, Har­ lignin was carried out by applying phloroglu­ togiella and Maurocenia is described and its cinol/hydrochloric acid directly to the bark taxonomie significance assessed. Although surface. placed under the Cassinoideae by Loesener Descriptive terms follow Whitmore (1962a, (1892, 1942), Pleurostylia, with its dry b), Roth (1981) and Van Wyk (1985). The fruits, is not considered to be closely related definition of inner bark foIlows Whitmore to the other southern African Cassinoideae. It (1962a). Terminology of the various scleren­ has therefore been excluded from this study. chymatous elements foIlows the proposals of Special emphasis is placed on bark features Parameswaran (1980). The terms conducting for evaluating previous proposals to subdivide and non-conducting phloem were replaced by Cassine s.l. into several, aIlegedly more na­ non-collapsed and collapsed phloem respec­ tural, genera (e.g. Loesener 1894, 1942; Rob­ tively as suggested by Trockenbrodt (1990). son 1965, 1966). Results Materials and Methods Barks of the investigated species can be Fifty-three sampIes of mature bark, from grouped into six distinct anatomical types. 16 species of Cassine s.l., Allocassine, Har­ The principal structural differences between togiella and Maurocenia were studied using the types are summarised in Table 1. Descrip­ mainly light microscopy. Voucher specimens tions of the various bark types, as weIl as the are housed in the H. G. W. J. Schweickerdt details of the taxa in which they are found, Herbarium (PRU) and listed under Results. are given below.

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Table 1. Summary of the diagnostic bark anatomical features in the six bark types recognised (+ = present; - = absent).

o(l o(l s:! s:! l:i i2 s:! ": <::l ~ -2 s:! erd ~-2 .~ Genera proposed by -c:t: :] .~ <::l ~ .5 ~ . ... Archer (1990): ~ ~ f t:i t: ] i: :2l ] ~\..) ~ J 8:il ~ ~

Bark type: Al A2 B C D E

Sclerenchyma Large primary sclereids + + Fibres + + Sclerenchyma absent in both non--collapsed and collapsed phloem + Chambered crystalliferous sclereids + + Crystals and other features Styloids + Septate crystal strands + Elastic threads + Cell width of widest phloem rays (near cambium) 6 6 4 3 1 (2) 1 (2) Periderm Sclerenchymatous phelloderm + Number of periderm layers 2-5 2-3 2-3 2-3 3-8 Persistent periderm +

Bark type Al (Figs. 1,7,9, 10, 15, 16,23, Ion Eck!. & Zeyh.): Archer 303,312,366.­ 24) C. matabelicum (Loes.) Steedman (alterna­ Diagnostic characters: Large fibre-sclereids tively placed under Elaeodendron Jacq. f.): and/or sclereids abundant throughout the sec­ Venter & Archer 184, 185. - C. papillosa ondary phloem; sclereids in the non-dilating (Hochst.) Kuntze (alternatively placed under phloem often clustered in fusiform groups Elaeodendron): Archer 217,224,344. - C. (radial longitudinal section), also in the dila­ transvaalensis (Burtt Davy) Codd (alterna­ tation zone (transverse section); phelloderm tively placed under Crocoxylon): Archer 215, crystalliferous and weakly sclerified, the 222, 245, 246, 325, Pienaar & Archer 1338. latter elements irregularly arranged, or in a General: Bark surface longitudinally fis­ more or less continuous ring; rhytidome weIl sured; fissures narrow to broad, often cutting developed. deep into the rhytidome layers. Bole grey to Material studied: Cassine crocea (Thunb.) brown, recently sloughed off flakes exposing Kuntze (alternatively(alternative1y placed under Crocoxy- bright orange patches of new periderm in C.

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. ~::::::::;::: •••_. oe~.-; ~ :,:.,- -...... R , ~- . ., ~ R .... ,;...... 4 .~ .. r .... _"", - .. -:,:- ...... ~.- -'" .. . • I,' ~ , -f•• ... ~ ~ ~ ::; ...... ,_...... ~ .c; . ~-;: ...... ,.., '. ~ -'-';'- " '!! " "" . ~ P , ...... , -. - - "' .. . ' ; ....: ...... ~ ... _ ..'~:' :fo•• j -: ....:...... ;,.~ - ..... "., ._.,.r-.. " ••,.;- ...... -;.a ...... , J- .... .-- .. -- 1/-' .. .' • • • 1 ; 41 ~ • "...... ;,.: - .- .-. .: .~, " •• ff·· ..... J. ... ", .. .-.'- tIfII' ""'~"'J.~ - .' ~ 0' .'~ ~ ••!,.. • ...... ,.':,,: ;'.... .; , " ,-: ,. I ...... -_. ..- J... .. ••. CP " ' "I ...... ' •••• CP " .;-­ .- .., .,.~ .'.,,'" .... _ '.w ... ~...... '~,Y•. rfl_ ~ •• ,..o·)! •• -p '" • •".1" ~- .- ".. -.. ..;- ~. - ~ i .' ...... ".:1 '''.: . .. • ", --~ . ,'r... •"Ic..." .,...... -". .~..... -- ..: , ...te. '''' ___.- · · ~ - .. __r._ .. ·--..,--- ···------... __.. t', I.teill ...... NP ,,, ..., • .a .,,.~/" - .:~,.,. .. ,..... •.... -..· ~ .~: - ~~!:~~•. ~ . ~ . ~.. __ .. ~~ - :-...... 1.. ~... • ... 2 - 1 - P

CP

CP NP

NP 4 - 3 - R ~- -,,­

-.. _._...... ~ - " P - - -~- ---- ___ CP ~ _. _ ...... u ..... __ u.u.u···.··_... u CP --...---..:--... =-- ...-..~ .. _---. ... .- ...... -...... -- ...... ---...... 5 6

Downloaded from Brill.com10/04/2021 12:50:06AM via free access Archer & Van Wyk - Bark of Cassinoideae 39 ------papillosa and C. crocea. Orange pigment also rays. Usually with a few sclerenchymatous visible when the outer bark surface is lightly elements mainly localised in the phelloderm. scraped; pigment absent or barely visible in Dilatation tissue either weakly developed C. transvaalensis. Slash red to pinkish, with as an irregularly widening of the rays owing a narrow greenish zone just inside the last­ to tangential enlargement and multiplication formed periderm. Inner bark width (sensu of ray cells, or, more usually, well developed Whitmore 1962a, b; Van Wyk 1985) (3-)5- as a broad continuous band of dilatation tissue 10(-13) mm. beneath the last-formed periderm (henceforth Anatomy: Sieve elements abundant, occur­ referred to as pseudocortex) in most sampIes. ring as narrow radial rows between the rays, Composed of mainly parenchyma cells which usually obliterated in the collapsed phloem. often tend to form conspicuous tangential Sieve plates strongly oblique; sieve areas 7-29 rows. Large tangentially elongated secondary per plate, equally spaced. Sieve areas occa­ sclereids or groups of sclereids (secondary sionally present on the lateral walls. Trans­ sclereids) present. verse to oblique anticlinal partitions common, Crystals prismatic; present in rays in non­ 2-4 per sieve element (secondary septation collapsed phloem, and in the dilated rays of of Zahur 1959). Companion cells narrow, the collapsed phloem. Crystalliferous cells occurring in short strands often next to the often present in the phelloderm. phloem rays. Axial phloem parenchyma not Periderms usually 2-5, formed sequenti­ observed or scanty. ally as discontinuous layers connected to the Phloem rays heterogeneous, uni- or multi­ older layers and usually overlapping. Peri­ seriate with the procumbent portion 4-6 cells derms continuous and curved, completely wide (before dilation). Uniseriate margins separating living tissues from dead. Phellem consisting of 2-5 layers of upright cells. stratified, usually composed of 2-5 layers of Course of rays more or less straight, before cells with pinkish stained (safranin/fast-green) dilating in more or less funnel-shaped pat­ tanniniferous contents alternating with 1 or 2 terns. layers of empty cells. In C. transvaalensis Fibres absent. Both large primary brachy­ composed of weakly defined layers of cells sclereids and fibre-like sclereids (fibre-scle­ with slightly thickened radial walls (stained reids) present. Sclereids present from the red with safranin/fast-green) alternating with borderline between the non-collapsed and uniseriate layers of thin-walled cells. Phello­ collapsed phloem, scattered as large individu­ derm parenchymatous with scattered scle­ al fusiform cells (fibre-sclereids) or clustered reids, assembled in irregularly shaped groups in axially fusiform (radially longitudinal sec­ or in a weakly developed sclerenchymatous tion) and regular round to square (transverse ring or rings to the inside of the phelloderm. sec ti on) groups. Sclereid groups in the col­ Crystalliferous cells often present. lapsed phloem axially elongate; usually ar­ Rhytidome nearly always present, consist­ ranged in weak concentric layers interrupted ing of (1-)2-4(-6) superposed sheet-like by rays in transverse aspect. Secondary scle­ layers, each 0.5-2.0 mm thick; each new reid groups in dilatation tissue tangentially periderm taking a deep course thereby pro­ expanded owing to lateral proliferation of the ducing a thick rhytidome layer.

Figs. 1-6. Schematic presentation of bark types, transverse section, sclerenchyma shown in black. - 1: Bark type Al, Cassine transvaalensis (Archer 215). - 2: Bark type A2, C. aethiopica (Archer 244). - 3: Bark type B, C. maritima (Archer 277). - 4: Bark type C, C. peragua (Van Jaarsveld 10581). - 5: Bark type D, Allocassine laurifolia (Van Wyk 8307). - 6: Bark type E, C. reticulata (Van der Walt s.n.). - Scale bars = 1 rum. - NP = non-collapsed phloem; CP = collapsed phloem; P = phellem; PD = phelloderm; R = rhytidome.

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Bark type A2 (Fig. 2) Dilatation tissue weil developed as a pseu­ docortex. Large isolated secondary sclereids or Diagnostic characters: Secondary sclereids tangentially elongated sclereid groups (groups relatively large, present throughout the sec­ more or less round in radial longitudinal sec­ ondary phloem (rare in non-collapsed phlo­ tion), abundant. Strongly tanniniferous. em); phelloderm parenchymatous, very rarely Crystals prismatic; present in rays of non­ sclerified (with isolated secondary sclereids) collapsed phloem, and abundantly so in the or crystalliferous; rhytidome weIl developed. collapsed phloem, occasionally in sclereids. Material studied: Cassine aethiopica Yirtually absent in phelloderm. Thunb.: Archer 212, 244, 247, 272, 324, Periderms usually 2-5, weil developed, 327,379. - C. burkeana Kuntze: Archer 210, formed sequentially as discontinuous layers 211. These taxa previously inc1uded in Mys­ connected to older layers and usually over­ troxylon Eck!. & Zeyh. sect. Eumystroxylon lapping. Periderms continuous and curved, Loes. completely separating living tissues from General: Surface longitudinally and trans­ dead. Structure of rhytidome obscured owing versely fissured; fissures narrow to broad, to inconspicuous periderm cells. Phellern not often cutting deep into the rhytidome layers. stratified, consisting of compressed cells with Bole grey. Orange pigment not observed but red (safranin/fast-green stained) walls. Phel­ lichens usually present. Slash red to pinkish, loderm parenchymatous, usually tanninifer­ with a narrow greenish zone just inside the ous with few isolated secondary sc1ereids and last-formed periderm. Inner bark width (3-) crystals scanty or absent. 5-8(-10) mm. Rhytidome weIl developed, consisting of Anatomy: Sieve elements with 6-19 sieve (1-)2-4(-6) superposed sheet-like layers, areas per plate, and copious slime present in each 0.5-2.0 mm thick; each new periderm the non-collapsed phloem. Otherwise as in taking a deep course thereby producing a bark type A I. Axial phloem parenchyma pres­ thick rhytidome layer. Periderm usually winds ent, inconspicuous, occurring in short strands round sclerenchymatous elements. ofaxially elongated thin-walled cells. Phloem rays heterogeneous, uni- or multi­ Bark type B (Figs. 3,20) seriate with the procumbent portion 3-6 cells wide. Uniseriate margin with up to 5 upright Diagnostic characters: Crystals present, sty­ cells. Course of rays more or less straight, be­ loids; elastic threads (trans-l,4 polyisoprene) fore dilating in irregular funnel-shaped struc­ present throughout non-collapsed and col­ tures. Starch grains often present in ray cells. lapsed phloem; sclerenchymatous elements Sc1ereids confined mainly to the collapsed absent in both non-collapsed and collapsed phloem and dilatation zone; scattered as giant phloem; phellern parenchymatous, rarely crys­ solitary cells (primary brachysclereids), or in talliferous. densely packed axially elongated (compact and Material studied: Cassine eucleiformis round in transverse section) groups. Scle­ (Eck!. & Zeyh.) Kuntze: Archer 233, 235, reids often crystalliferous. Secondary sc1ereid 236, 240. - C. maritima (H. Bol.) L. Bol.: groups in dilatation tissue tangentially elon­ Archer 265,277, Yan Greuning 628. These gated (transverse section). Phelloderm not taxa previously included under Mystroxylon sc1erified, rarely with isolated sc1ereids. sect. Pseudoscytophyllum Loes.

Figs. 7-12. Non-collapsed secondary phloem as seen in transverse and longitudinal section. - 7: Cassine crocea (Archer 366), transverse section. - 8: C. tetragona CYan Wyk 8276), trans­ verse section. - 9 & 10: C. transvaalensis (pienaar & Archer 1338); 9: transverse section; 10: sieve elements in tangential section, note sieve plates. -11: Allocassine laitrifolia CYan Wyk 8307), fibres and septate phloem elements in radial section. - 12: Mauroceniafrangularia CArcher 261), sieve plates taken under fluorescence optics. - Scale bars = 20 )lm.

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Figs. 13-16. Sclerenchymatous elements in inner bark. - 13: Cassine peragua (V an Jaarsveld 10581), fibres in transverse section. - 14: Allocassine laurifolia (Van Wyk 8307), fibres in transverse section. - 15 & 16: Cassine transvaalensis (Pienaar & Archer 1338), fibre-sclereids; 15: transverse section; 16: radial section. -- Scale bar = 20 ~m.

General: Bark surface longitudinally and Anatomy: Sieve areas 7-15 on lateral walls, transversely fissured; fissures narrow to of various sizes and irregularly arranged. broad, often cutting deep into the rhytidome Sieve elements otherwise sirnilar to bark type layers. Bole grey, orange pigment not ob­ Al. Elastic threads (trans-l,4 polyisoprene ) served, epiphytic lichens or algae usually present when pieces of bark are pu lied apart, present. Slash red to pinkish, with a narrow present in latex tubes in the non-collapsed greenish zone just inside the last-formed and collapsed phloem, absent in dilatation tis­ periderm. Elastic threads visible when a piece sue. Axial phloem parenchyma scanty, incon­ of bark is broken and pulled apart. Inner bark spicuous, 3-4(-7) cells per strand. Styloids width 2-4 mm. sometimes present in axüi! parenchyma cells.

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Figs. 17-20. Crystalliferous tissue. - 17 & 18. Cassine retieu/ata (Van der Walt s.n.), lignified chambered crystalliferous strands; 17: transverse section; 18: radial section, under polarised light. - 19: C. tetragona (Van Wyk 8276), lignified crystalliferous strands in radial section. - 20: C. eucleijoTmis (Archer 235), styloid crystals in non-collapsed phloem, under polarised light. - Scale bar =20 ~m.

Phloem rays heterogeneous, procumbent less straight, irregularly dilating towards the portion 2-3(-4) cells wide. Uniseriate mar­ pseudocortex. gins consisting of 1-3 rows of large upright Small solitary secondary sc1ereids scatter­ cells. Short uniseriate rays of upright cells ed in dilatation tissue in C. eucleiformis. Scan­ usually present. Styloid crystals often present ty in C. maritima. Scattered solitary or irreg­ in upright portion of uniseriate rays and uni­ ularly dispersed groups of tangentially elon­ seriate margins ofmultiseriate rays. Ray cells gated secondary sclereids confined to dilating thin-walled and usually tanniniferous; some rays and dilatation tissue. Sc!ereids absent or of the cells tangentially e10ngate and lignified scanty in phelloderm. in the dilatation zone. Course of rays more or Dilatation tissue weIl dcve1oped, continu-

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Figs. 21-24. Phellem structure. - 21: Cassine parvifolia (Archer 296), stratified phellem with layers ofradially elongated cells. - 22: C. barbara (Yan Wyk AI138), stratified phellem with layers of phellem cells with thick lignified walls alternating with loosely arranged thin-walled cells. - 23: C. transvaalensis (Archer 245), slightly stratified phellem. - 24. C. papillosa (Archer 217), homogeneous phellem. - Scale bar = 20 !lm. ous as a pseudocortex beneath the last-form­ tiseriate rays (Fig. 20). Sparsely seattered ed periderm, inwardly interdigitating with the styloids observed in dilatation tissuc. Pris­ seeondary phloem. Composed mainly of a matie erystals also present - apparently re­ matrix of parenehyma cells interspersed with placing the styloids, either randornly distri­ solitary or small irregular groups of tangenti­ buted or mainly in weak radiallines in dilated ally dilated secondary sclereids as weil as the rays and pseudoconex. Crystals virtually ab­ remains of obliterated phloem elements. sent in phellodenn. Styloid erystals abundant in the non-col­ Periderms one or more (no well-preserved lapsed phloem, occurring in axial parenchy­ sampIe of rhytidome available), sequential ma cells, uniseriate rays and margins of mul- periderms as in bark type ALPhellem not

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stratified, composed of thin-walled suberised the dilatation zone (dilation irregular, with a ceIls usuaIly with tanniniferous contents (stain sharp transition between collapsed phloem red with safranin/fast-green; spots of a col­ and pseudocortex in C. parvifolia). ourless substance which shows birefringence Fibres usually present in non-collapsed and under polarised light present in C. eucleifor­ collapsed phloem, often appearing elose to the mis). Phellern thicker and consisting mainly cambium; sometimes with only a single weak­ of red-stained tanniniferous phellern cells in ly tangentially developed layer of fibres pro­ C. maritima. Phelloderm weIl developed, pa­ duced elose to the vascular cambium. Groups renchymatous, sclereids and crystals scanty of small isodiametric selereids present in di­ or absent. lated rays adjacent to fibres or in pseudo­ Rhytidome weakly developed, l-2layers cortex. Absent or scanty in phelloderm. observed. Periderm layers appear to break Dilatation tissue weakly or weIl developed. off at a rapid rate. Crystals prismatic; solitary crystaIIiferous cells randomly distributed in rays. Occasion­ ally present in phelloderm. Bark type C (Figs.4, 13,21, 22) Periderms one or two. Phellern usually Diagnostic characters: Fibres usually pres­ stratified, composed of 2-4(-5) weakly de­ ent; phellern usually stratified, layers of cells fined multiseriate layers of thin-walled suber­ with thick lignified walls alternating with ised cells alternating with 2-5 layers of cells loosely arranged thin-walled cells; phello­ with thick, lignified walls, usually with U­ derm parenchymatous, occasionally crystalli­ shaped thickenings. Cells with red (safranin/ ferous; bark relatively thin. fast-green) tanniniferous substance scattered Material studied: Cassine barbara L.: Ar­ in phellern. Stratified cork with radially elon­ eher 264, Van Wyk Al 138. - C. parvifolia gated thin-walled cells present in some sam­ Sond.: Archer 296, Van Greuning 627. - C. pies of C. barbara and C. parvifolia. Layers peragua L.: Archer 238,239,285, Van Jaars­ ofregular thin-walled suberised cells alternate veld 10581, 10583. - Hartogiella schinoides with broad layers of loosely arranged radially (Spreng.) Codd: Archer 251, 252, 258, Van elongated (slender and filamentous) cells and Jaarsveld 10580, 10582. usually tanniniferous. Phelloderm parenchy­ General: Bark flaky, portions (layers) of matous, weakly developed, crystals occasion­ rhytidome weathering away, exposing an ally present, selereids absent or scanty. orange pigment in C. peragua and H. schinoi­ Rhytidome weakly developed, 1-2 sheet­ des; pigment also visible when bark surface like, 0.5-1 mm thick layers observed. is lightly scraped. Orange pigment barely dis­ cernible or absent in C. barbara and C. parvi­ Bark type D (Figs. 5, 11, 14) folia. Slash pinkish red, with a narrow green­ ish zone just inside the last-formed periderm. Diagnostic characters: Fibres present; phel­ Inner bark width 1.5-3 mm. loderm crystalliferous; rhytidome absent with Anatomy: Sieve areas 3-17(-25) perplate. periderms not formed sequentiaIly. Sieve elements with up to seven transverse Material studied: Allocassine laurifolia divisions present per element, otherwise sim­ (Harv.) N.K.B. Robson: Van Wyk 8307, ilar to bark type Al. Axial phloem parenchy­ 8397. ma scanty and inconspicuous. General: Phellern with a conspicuous orange Phloem rays heterogeneous, procumbent pigment. Surface more or less smooth. Inner portion 2 or 3 cells wide. Uniseriate margins bark width 1-1.5 mm. of 1-3layers of upright cells. Uniseriate rays Anatomy: Sieve areas 10-17 per plate. Ele­ of upright cells usually present. Ray cells ments subdivided by 3-4(-5) transverse to thin-walled and tanniniferous, often becom­ oblique anticlinal walls. Companion cells in ing partially Iignified adjacent to fibre bun­ strands of 1-3 cells. Otherwise similar to bark dies. Course of rays more or less straight, type Al. Axial phloem parenchyma scanty dilatation more or less funnel-shaped towards and inconspicuous.

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Phloem rays heterogeneous, uniseriate or Anatomy: Sieve areas 9-22 per plate. Ele­ sometimes with a short biseriate upright por­ ments with 3-7 oblique to very oblique anti­ tion. Regular course ofrays rapidly disrupted clinal walls, and usually two or three relatively at border between non-collapsed and collapsed short companion cells. Axial phloem paren­ phloem. chyma scanty to absent. Fibres already present elose to the cam­ Phloem rays heterogeneous, uniseriate or bium, single or in irregular groups. Isodia­ biseriate; composed predominantly of square metric small selereids present in dilated rays cells, with short uniseriate margins. Course adjacent to fibres. Sclereids absent in phello­ of rays more or less straight (irregular with a derm. sharp transition between collapsed phloem Dilatation tissue weil developed, as a nar­ and pseudocortex in C. tetragona). row zone of pseudocortex beneath the peri­ Sclereids in irregular to weil defined tan­ derm; collenchyma groups localised. gential or concentric bands in collapsed phlo­ Crystals prismatic; confined to rays and em. The bands composed of densely packed dilatation tissue. Smaller prismatic crystals lignified chambered crystalliferous strands. A usually present in phelloderm. single prismatic crystal present in each cham­ Periderm persistent with no sequential peri­ ber. These bands interrupted only by rays. derm formation observed. Phellern exception­ Sclereids absent in phelloderm. ally thick, equalling the inner bark in thick­ Dilatation tissue present as narrow zone ness, composed of thin-walled suberised (pseudocortex) beneath the last-formed pe­ cells without visible contents. Phelloderm riderm. Collenchyma groups occasionall y weil developed, 5-8 celllayers thick, crys­ present. talliferous. Sclereids absent or scanty. Crystals prismatic; long parenchymatous Rhytidome absent, no sequential periderm or sclerified axial chambered crystalliferous formation observed. strands present in the phloem. Single crystals or crystalliferous strands particularly abun­ Bark type E (Figs. 6, 8, 12, 17-19) dant in M. jrangularia. Phelloderm weil de­ Diagnostic characters: Selereids in contin­ veloped, crystalliferous. uous bands of densely packed chambered Periderm usually represented by (2-)5-8 crystalliferous strands; rays composed of pre­ sequential periderms, formed as discontinu­ dominantly square cells; phelloderm crystalli­ ous layers connected to the older layers and ferous; rhytidome weil developed and rami­ usually overlapping, completely separating fied; C. tetragona is peculiar in its liana stern living tissues from dead. Phellern stratified, structure with deeply penetrating wedge­ composed of 2-4(-5) weakly defined layers shaped secondary phloem inclusions in the of thin-walled suberised cells alternating with wood (Archer 1990). 2-5 layers of slightly lignified cells with Material studied: Cassine reticulata (Eckl. weakly developed U -shaped thickenings. & Zeyh.) Codd: Archer 313, Van der Walt Phelloderm weil developed and crystallifer­ s.n. (previously included in Lauridia Eckl. & ous. Sclereids absent. Zeyh.). - C. tetragona (L. f.) Loes.: Archer Rhytidome weil developed, with (2-)4-8 273, Van Wyk 8276. -Mauroceniajrangula­ (only 2-3 in C. tetragona) sheet-like layers, ria (L.) Mill.: Archer 259, 261, Van Wyk each c. 0.2 mm thick; formed by a network A1066. of periderms, each new periderm taking a General: Bark flaky and rough, cracked in shallow course, thereby producing a thin a grid-like pattern, continuously exfoliating rhytidome layer. in small pieces owing to weathering. Newly exposed areas of bark with a yellow pigment Discussion in C. reticulata and M.frangularia (observed only on root bark of C. tetragona). Slash General pinkish, with a narrow greenish zone just Sloughing off and surface patterns of bark beneath the innermost periderm. Inner bark were sirnilar in all the sampies of Cassine S.l. 1-2mm wide. studied. In photographs taken of sterns of

Downloaded from Brill.com10/04/2021 12:50:06AM via free access Archer & Van Wyk - Bark of Cassinoideae 47 species of Cassine, no constant or conspicu­ of C. eucleiformis (Coates Palgrave 1983). ous differences were noticed except in Allo­ The threads consist of trans-1 ,4-polyisoprene cassine. Sterns of A. laurifolia lack a rhyti­ and are produced in laticifer-like cells ('latex dome and are covered by a thick layer of tubes') or possibly in sieve elements (Drennan orange-green phellern which makes it possi­ et al. 1987). There is no cytoplasm visible ble to distinguish this bark from all the other within these rubber-containing tubes, indicat­ sampies investigated. ing an atypical laticifer ultrastructure. The Orange pigments are present in most of presence of elastic threads has been reported the species, and are deposited in the phellern. in many members of the Celastraceae and Rhytidome layers separate from each other Hippocrateaceae in other parts of the world by the splitting of the phellern tissue, thus (Blakelock 1951; Hou 1962; Hall & Lock displaying pigments in the freshly exposed 1975). EIsewhere in the Ce1astraceae laticifer­ phellern surfaces. The bright orange pigment like tubes are confined to stern and bark in the bark of various species of Cassine s.l. in species of Euonymus, while in species has often been used as a diagnostic field char­ of Wimmeria the tubes also occur in the acter in general identification guides and keys leaf (Solereder 1908). No detailed studies (Palmer & Pitman 1973; Coates Palgrave have been made on the structure of these 1983). Presence of pigment is also reflected tubes in the Celastraceae. They are not ex­ in some of the common names for the group: plored in this study, but require closer exami­ Bastard saffronwood (C. peragua), Common nation. saffronwood (C. papillosa), Red saffronwood Total bark width was strongly influenced (C. crocea) (Coates Palgrave 1983). Pigment by the rate of rhytidome sloughing. The abundance varies considerably between dif­ width of inner bark (in the sense of Whitmore ferent individuals and populations of a spe­ 1962a, b) only was considered. Bark types cies, and is also affected by the degree of C, D and E are characterised by a relatively weathering. Orange pigment is very conspic­ thin (1.5-3 mm) inner bark. Roth (1981) uous in forest trees of C. papillosa and C. considered the occurrence of a thin bark (1-3 peragua owing to faster sloughing off of the mm) as rare amongst tropical species. Bark rhytidome layers. In most species of Celas­ types Al, A2 and B are characterised by an traceae (including Hippocrateaceae) variable inner bark wider than 5 mm. amounts of orange pigment may be present in different parts of aplant, e. g. twigs, sterns Sieve elements or root (Schlechter & Haller 1942; Krishna­ The relatively thick bark sections used in moorthi et al. 1962; Johnson et al. 1963; Heg­ this study were not entirely suitable for the nauer 1964; unpublished observations). Heg­ examination of sieve elements. It is, never­ nauer (1964) reported the presence of pristi­ theless, clear that the morphology of these merin and celastrol, two yellow pigments, in elements conforms to the published informa­ the bark of various species of Celastraceae. tion on celastraceous phloem (Zahur 1959, in The presence of these pigments appears to be Appendix). diagnostic at the family level. The sieve elements (type II in Zahur 1959), The slash of all the investigated species discernible in the non-collapsed phloem, are varies from red to pinkish or light brown, more or less similar in the different bark types. and no significant interspecific differences The only conspicuous difference is in the were noticed. If the periderm is scraped to number of sieve areas per plate. Zahur (1959) expose the outer edge of the phloem, a green­ was the first to report the widespread occur­ ish zone of tissue is usually revealed. The rence of secondary septation of phloem ele­ green pigment (chlorophyll) is located in the ments in the dicotyledons, including Celas­ phelloderm and dilatation tissue. traceae. Esau (1969) interpreted these as The presence of elastic threads in species anticlinal divisions, but later (Esau 1979) de­ with bark type B, revealed by breaking part signated them secondary partitions. These of the leaf, stern or bark, is often used as a anticlinal divisions are usually present in the diagnostic field character for the identification sieve elements of a1l species investigated.

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Companion cells were observed to usually is nevertheless possible to distinguish between be short strands of (1-)2-4(-5) cells, adja­ fibres, fibre-sclereids, sclereids and lignified cent to the sieve tube elements. They are small parenchyma cells in the investigated celastra­ and difficult to recognise in thick sections. ceous bark sampIes. Fibres are present in bark types C and D. Axial phloem parenchyma In transverse section, a fibre is recognised as Phloem parenchyma cells are usually scan­ a circular, or tangentially flattened cell with a ty. These cells were difficult to discern in the small lumen. The cell wall is thick, lignified relatively thick sections used, and it is not and not polylamellate. Pit size varies from possible to detail their structure. minute to smalI, c. 3 ~m in diameter. The fibres are randomly scattered as single cells, Phloem rays arranged in irregular groups or in thin, weak­ Ray structure is heterogeneous, either uni­ ly developed tangential bands. seriate or multiseriate, with the procumbent Fibre-selereids are restricted to bark type portion up to seven cells wide. Uniseriate Al. They develop in or elose to the non-col­ margins of multiseriate rays are composed of lapsed phloem. These elements do not com­ (1-)2-5(-7) mostly upright cells. Bark type ply with the definitions of either fibres or E has usually uniseriate rays composed of selereids and are intermediate between the predominantly square cells, distinguishing it two. Fibre-selereids have polylamellate walls from the other types. The usefulness of this and are radially elongate with blunt ends. character is limited by difficulty in interpret­ Alternating concentric bands of densely ing ray cell shape in bark sections. More data packed chambered crystalliferous strands of are needed to establish the taxonomic signifi­ selereids with a solitary prismatic crystal in cance of this feature in the Celastraceae. The each chamber were found in bark type E. It is rays are composed of thin-walled, non-ligni­ not elear from this study whether this type of fied (at least initially) cells which are usually selereid develops from the subdivision of a tanniniferous and/or often crystalliferous. In long initial cell or through division of an iso­ the dilatation tissue ray cells, traversing diametric parenchyma cell (Bailey 1961; Para­ groups of selerenchymatous elements may meswaran & Richter 1984). For example, sometimes become selerosed (bark types C, Bailey (1961) described how a selereid initial D, and E). In the dilatation zone, rays dilate becomes compartmentalised by septa and dif­ by cell division and tangential cell extension ferentiates into achambered selereid initial owing to tangential stretching stresses. cello Some of these new sclereid initials repeat With the exception of slight variation in the process to produce astrand of sclereids. the width, course and dilation of the rays, no Ontogenetic studies are needed to clarify the constant interspecific differences in ray mor­ origin of the observed chambered crystallifer­ phology were noticed. ous strands of sclereids in Celastraceae. Tan­ gential bands of similar axially elongated Sclerenchymatous elements chambered crystalliferous strands were also Mechanical tissue in the form of seleren­ observed in two species of Catha Forsk. ex chymatous elements is usually the taxonomi­ Scop. (unpublished results). cally most significant pattern-producing tissue Sclereids were usually recorded in all the in the bark (Chattaway 1953; Roth 1981). examined species of Allocassine, Cassine, Although the selerenchymatous elements may Hartogiella andMaurocenia. A distinction was vary considerably in size, form and distribu­ made between primary and secondary brachy­ tion in different sampIes of the same species, sclereids on the basis of their origin. Primary they can be used extensively for the delimita­ sclereids are present in the non-collapsed sec­ tion of the various bark types in the investi­ ondary phloem, elose to the vascular cambium gated material. or early in the collapsed phloem, and are char­ No absolute criteria are known to separate acteristic of bark types Al and A2. In trans­ sclereids from fibres (Esau 1969). According verse sections of bark these selereids are scat­ to the definitions of Parameswaran (1980), it tered as larg

Downloaded from Brill.com10/04/2021 12:50:06AM via free access Archer & Van Wyk - Bark of Cassinoideae 49 irregular, round or square superposed groups. cal studies. However, two types of crystals, A weakly defined tangentiallayering ofparen­ prisms and styloids, were observed in the chymatous and sc1erenchymatous zones was bark of the investigated species. seen in most sampIes of bark types Aland Prismatic crystals are scattered in the bark, A2. The sc1erenchymatous zones occasion­ with a tendency to be much more abundant in ally become a continuous ring of sc1ereids ray cells and phelloderm in eertain bark types. interrupted only by rays. They frequently develop in parenehyma eells Secondary sc1ereids usually arise late in the eontiguous with sc1ereids and within sc1e­ collapsed phloem and in the dilatation tissue. reids. Strands of ehambered erystalliferous These sc1ereids develop from parenchyma sclereids are present in Cassine reticulata, C. cells and are usually characterised by a rela­ tetragona and Maurocenia frangularia (bark tively large size, 'and polylamellate lignified type E). Crystals and erystalliferous sc1ereids cell walls. Numerous simple (often branched are partieularly abundant in C. reticulata and or ramified) pits and a distinct celllumen are M.frangularia (Figs. 17-19). present. These sc1ereids vary in number, size Styloid crystals are eommon in the fune­ and shape and are irregularly dispersed as tional phloem of Cassine eucleiformis and C. single cells or groups of sc1ereids. Cell en­ maritima (bark type B), where they are found largement usually takes place in a tangential in the axial parenehyma eells and in the uni­ direction owing to tangential stretching in the seriate marginal eells of rays. The presenee of dilatation tissue. Secondary sc1ereids were styloids is taxonomieally important beeause found in most of the sampIes studied and seem this erystal type oeeurs infrequently in bark. to possess no taxonomie value. For example, Roth (1981) reported styloids Lignified ray parenchyma cells are sporadie in bark of only a few species of two of the 48 in the dilating rays, collapsed phloem and dila­ families she investigated. Baas (1975) report­ tation tissue of bark types C, D and E. These ed styloids in the bark of Sphenostemon Bail!. cells develop from ray parenchyma cells (Aquifoliaceae) and used their presenee as an which are in contact with sc1erenchymatous important eharaeter in the diseussion of pos­ elements. They are usually tanniniferous and sible taxonomie affinities of the genus. Sty­ sometimes tangentially elongated. loids are also present in the bark of some of the thomless southern African species of May­ Dilatation tissue tenus Molina and in Pseudosalacia streyi This tissue is usually present as the result Codd (unpublished results). Henee, the pres­ of ray cell enlargement and multiplication. ence of styloids remains a distinetive taxon­ Dilatation tissue is present as a widening of omie feature to be taken into aecount in future rays or as a broad continuous band of paren­ bark anatomical work on other eelastraeeous chymatous cells beneath the last-formed peri­ taxa. derm. This zone corresponds to the pseudo­ cortex of Whitmore (1962a, b), Roth (1981) Periderm and Van Wyk (1985). Large secondary sc1e­ Periderm strueture is often negleeted in reids, occurring singly or in irregular groups, bark anatomical studies. Features found to be are usually present. Tangential expansion of taxonomieally useful in the present study in­ parenchyrna cells and sc1ereids were frequent­ clude the presenee of a homogeneous or strat­ ly observed. Prismatic crystals are abundant ified phellem and a sclerified phelloderm. in the dilatation tissue, either randomly scat­ The stratified phellem eonsists of eells with tered or in a tangential arrangement. U-shaped thiekened eell walls altemating with layers of thin-walled eells, whieh may be tan­ Calcium oxalate crystals niniferous or empty. Layers of thin-walled, Calcium oxalate crystals are a very com­ radially elongated eells also eontribute to the mon feature of the secondary phloem (Zahur stratifieation of the phellem. 1959; Esau 1969; Roth 1981). In fact, crys­ The stratified phellem with lignified or tals are so common in bark that they are usu­ elongated eelllayers (as',jn Cassine barbara, ally not taken into account in bark anatomi- C. peragua and C. parvifolia) is useful for the

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recognition of bark type C. According to Roth of Celastraceae for the Flora Zambesiaca re­ (1981), lignification of cork cells is probably gion, recognised five genera in Cassine s.l., more effective than suberisation in a humid name1y Cassine s.str., Elaeodendron, Mys­ tropical forest environment, since it gives troxylon, Crocoxylon, and Allocassine. Lau­ better protection to the bark against fungal ridia was included in Elaeodendron on account and bacterial attack. The southern African spe­ of some shared macromorphological charac­ cies with bark type C (especially C. peragua) ters. Of the aforementioned genera, only Allo­ are often associated with forests or humid cassine (p.p.), Cassine s.l., Maurocenia and environments. Hartogiella have been upheld in recent years The presence of a weakly sclerified phello­ (Codd 1966; Gibbs Russell et al. 1987). All derm in bark type Al is considered taxonom­ sources of evidence investigated (Archer ically important, although its degree of devel­ 1990; Archer & Van Wyk 1992; Den Hartog­ opment may show considerable variation. Van TerTholen & Baas 1978) provide un­ Nevertheless, it is one of the main diagnostic equivocal taxonomic criteria for distinguish­ characters of this bark type, distinguishing it ing between a number of genera. from the very similar type A2. More bark The species with bark type Al fall within sampies of Celastraceae need to be studied to the concept of the genera Elaeodendron and fully evaluate the taxonomic significance of Crocoxylon. An extra-African species of this tissue. The crystalliferous phelloderm, Elaeodendron (E. quadrangulata) also dis­ often present in bark types A, D and E, is very plays this bark type (unpublished results). distinctive and allows them to be distinguish­ The species with bark type Al can usually be ed from the other types. told apart by slight variations. It is, however, not possible to consistently distinguish be­ Rhytidome tween the closely related Elaeodendron and A well-developed rhytidome occurs in bark Crocoxylon on the basis of this variation. types Al, A2 and E. In bark type E the second­ The well-delimited genus Crocoxylon can, ary phloem/rhytidome ratio is 1:1. The bark however, be distinguished from Elaeodendron of many species in forest environments is fre­ by its pollen structure and peculiar floral char­ quently covered with epiphytic mosses and acters (Archer 1990; Archer & Van Wyk lichens. The absence of a conspicuous rhyti­ 1992). Exarnination of more bark of African dome in many of the sampies could perhaps and also the Asiatic species of Cassine s.1. be ascribed to weathering conditions. Bark will be necessary to fully assess the taxonom­ type D (Allocassine) is distinct in always ie status of Elaeodendron and Crocoxylon. having only one periderm accompanied by a Species formerly placed in Mystroxylon thick and conspieuous phellern. display two distinct types of bark; A2 and B. These conform to a previous subdivision of Taxonomie eonelusions the species in Mystroxylon (Loesener 1942). Although studies of bark anatomy have The species with bark type A2 correspond not been carried out on a wide enough sc ale to the species in the section Eumystroxylon to fully evaluate the taxonomic significance of Loes. and are characterised by large second­ the observed diversity in bark structure, our ary sclereids. Mystroxylon, as defined by observations are extremely useful for the sub­ Archer (1990), is distinguished by constantly division of the southern African fleshy-fruited alternate leaves, pubescence and several ana­ Celastraceae. The diversity in bark structure tomical features. encountered in the study provides significant Species with bark type B conform to Loese­ support for the recognition of a number of ner's Mystroxylon sect. Pseudoscytophyllum small segregate genera as proposed by some (Loesener 1942). These species are unique in authors, e.g. Loesener (1894, 1942) and possessing styloid crystals and elastic threads, Robson (1965). The different bark types show and in lacking primary sclerenchymatous ele­ remarkable congruence with the generic de­ ments. Cassine eucleiformis can usually be dis­ limitation of Loesener (1942) and Robson tinguished from C. maritima by the presence (1965). Robson (1965,1966), in his revision of small secondary sclereids in the dilatation

Downloaded from Brill.com10/04/2021 12:50:06AM via free access Archer & Van Wyk - Bark of Cassinoideae 51 tissue. A new genus, which still requires for­ Acknowledgements mal description, is proposed for these two spe­ We are grateful to Dr. J.V. van Greuning, eies (Archer 1990; Archer & Van Wyk 1992). Mr. E. van Jaarsveld and Mr. N. van der Walt Cassine, as defined in a narrow sense by for collected bark sampies and to Miss G.L. Robson (1965), comprises two southern Afri­ Day for her critical reading andimprovement can species only, namely C. peragua (nomen­ of the manuscript. This study was supported cIatural type) and C. parvifolia. Robson con­ in part by research grants from the Founda­ sidered C. barbara to be congruent with C. tion for Research Development and the Uni­ peragua. Furthermore, Codd (1966) has ex­ versity of Pretoria. pressed doubts as to the generic status of Hartogiella (= Hartogia Thunb. ex L. f. non L.), a genus hitherto considered to be distinct References on the basis of seed characters. However, H. Archer, R.H. 1990. The taxonomie status of schinoides is characterised by bark type C, a Cassine L. s.l. (Celastraceae) in southern character shared with C. barbara, C. peragua Afriea. M.Sc. Thesis, University of Pre­ and C. parvifolia. The overall morphological toria. and anatomical similarity of the species with Archer, R.H. & A.E. van Wyk. 1992. Paly­ bark type C supports their indusion under nology and intergeneric relationships in Cassine s. str. (Archer 1990). Since C. pera­ some southern African species of subfam­ gua is the nomenclatural type ofthe genus Cas­ ily Cassinoideae (Celastraceae). Grana 31: sine, this step will necessitate name changes 241-252 .. for at least some, if not all, species of Cassine Baas, P. 1975. Vegetative anatomy and the s.l. from other parts of the world. affinities of Aquifoliaceae, Sphenosternon, Robson (1965) first described Allocassine PheIline, and Oneotheca. Blumea 22: 311- to accommodate the species A.laurifolia and 407. A. tetragona (L. f.) N.K. B. Robson. Allo­ Bailey, LW. 1961. Comparative anatomy of cassine is upheld by Codd (1966) and Gibbs the leaf-bearing Cactaceae, II. Structure Russell et al. (1987) as a monotypic genus, and distribution of scIerenchyma in the induding only A.laurifolia. The above-men­ phloem of Pereskia, Pereskiopsis and tioned authors prefer to treat A. tetragona as a Quiabentia. J. Arnold Arbor. 10: 144- species of Cassine s.l. The marked distinction 156. in bark structure between these two species Blakeloek, R.A. 1951. A synopsis of the supports their view. Allocassine laurifolia genus Euonymus L. Kew BuH. 1951: differs from all the other investigated species 210-290. by the absence of a rhytidome. Cassine tetra­ Chattaway, M.M. 1953. The anatomy of bark. gona occupies a fairly isolated position but L The genus Eucalyptus. Austral. J. Bot. shares bark type E with C. reticulata and 1: 402-433. Mauroceniajrangularia. On the basis of gen­ Chung, M.H. & C.W. Park. 1975. Studies eral anatomy and aspects of macromorphol­ on the development of antihypertensive ogy, the two last-mentioned species are clear­ agents from Korean emde barks. 1. Mor­ ly very similar, and are separated from each phological comparisons of Korean and other only by the mode of attachment of Chinese barks of Eucommia ulmoides and ovules (Archer 1990). of Euonymus japonicus in Korea and Euo­ This study has cIearly shown that bark ana­ nymus pellucidifolia in Taiwan. Korean J. tomical features are extremely usefuI for elu­ Pharmacogn. 6: 29-34. cidating taxonomie relationships between the Coates Palgrave, K. 1983. Trees of Southern southern African species of Cassine s.l. Fur­ Africa. 3rd impression. Struik Publishers, ther studies of the bark anatomy of members Cape Town. of the Celastraceae, and in particular species Codd, L. E. 1966. Celastraceae. The Cassine of Cassine s.l. from other parts of the world, complex. In: New and interesting records are essential to cIarify the infrafamilial taxon­ of African flowering plants. Bothalia 9: omy of the family. 123-151.

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Davison, J.D. 1927. Celastraceae. Bothalia Kostermans, A. J. G. H. 1986. Notes on 2: 289-346. Asiatic Cassine L. (Celastraceae). Gdns' Drennan, P.M., S.E. Drewes, J. Van Staden, BuH., Singapore 39: 177-191. S. MacRae & C.W.S. Dickens. 1987. An Krishnamoorthi, V., J. D. Ramanathan & anatomical, phytochernical and ultrastruc­ T.R. Seshadri. 1962. Constitution of tin­ tural characterization of the 'elastic threads' genone, a component of the stern bark of ofMaytenus acurninata. S. Afr. J. Bot. 53: Euonymus tingens Wal!. (F. Celastraceae). 17-24. Tetrahedron Lett. 23: 1047-1050. Dyer, R.A. 1975. The genera of southern Loesener, T. 1892. Celastraceae. In: A. Eng­ African flowering plants. 1. Departrnent of ler & K. Prant! (eds.), Die natürlichen Agricultural Technical Services, Pretoria. Pflanzenfamilien. Ed. 1, 3, 5: 189-222. Esau, K. 1969. The phloem. Handbuch der W. Engelmann, Leipzig. Pflanzenanatomie. V Gebr. Borntrae­ 12. Loesener, T. 1894. Celastraceae africanae. ger, Berlin. III. Bot. Jb. 28: 150-161. Esau, K. 1979. Phloem. In: C.R Metcalfe & L. Chalk (eds.), Anatomy of the dicotyle­ Loesener, T. 1942. Celastraceae. In: A. dons. Ed. 2, Vo!. 1: 181-189. Clarendon Engler/H. Harms & J. Mattfeld (eds.), Die Press, Oxford. natürlichen Pflanzenfamilien. Ed. 2, 20b: Eschrich, W. & H. B. Currier. 1964. Identi­ 87-197. Duncker & Humblot, Berlin. fication of callose by its diachrome and Mabberley, D.J. 1987. The plant-book. A fluorochrome reactions. Stain Techno!. 39: portable dictionary of the higher plants. 303-307. Cambridge University Press, Cambridge. Gibbs RusselI, G.E., W.G. Welman, E. Re­ McLean, RC. & W.R. Ivimey-Cook. 1941. tief, K.L. Immeiman, G. Germishuizen, Plant science formulae. McMillan & Co. B.J. Pienaar, M. Van Wyk, A. Nicholas, Ltd., London. C. De Wet, J.C. Mogford & J. Mulvenna. O'Brien, T.P. & M.E. McCully. 1981. The 1987. List of species of southern African study of plant structure: Principles and se­ plants. Ed. 2, 2, Part 2. Mem. Bot. Surv. lec ted methods. Termarcarphi (Pty) Ltd., S. Afr. 56: 1-270. Melbourne. Hall, J.B. & J.M. Lock. 1975. Use of veg­ Palmer, E. & N. Pitman. 1973. Trees of etative characters in the identification of South Africa. H. Balkema, Cape Town. species of Salacia (Celastraceae). Bois­ Parameswaran, N. 1980. Some remarks on siera 24: 331-338. the nomenclature of fibres, sclereids and Hartog-Van Ter Tholen, RM. & P. Baas. fibre-sclereids in the secondary phloem of 1978. Epidermal features of the Celastra­ trees. IAWA Bull. n.s. 1: 130-132. ceae s.!. Acta Bot. Neer!. 27: 355-388. Hegnauer, R. 1964. Chemotaxonomie der Parameswaran, N. & H.-G. Richter. 1984. Pflanzen. III. Birkhäuser Verlag, Basel. The ultrastructure of crystalliferous cells Hou, Ding. 1962. Celastraceae I, II. In: Flora in some Lecythidaceae with a discussion Malesiana Series I, 6: 227-421. of their terminology. IAW A Bull. n. s. 5: Jensen, W.A. 1962. Botanical histochemis­ 229-236. try. W.H. Freeman & Co., San Francisco. Robson, N.K.B. 1965. New and little known Jessup, L.W. 1984. Celastraceae. In: Flora species from the Flora Zambesiaca area of Australia 22. Austral. Gov. Publ. Serv., XVI, taxonomic and nomenclatural notes Canberra. on Celastraceae. Bolm Soc. Broteria. 39 Johansen, D.E. 1940. Plant microtechnique. (ser. 2): 5-55. McGraw-Hill Book Co. Inc., New York. Robson, N. K. B. 1966. Celastraceae (incl. Johnson, A.W., P.F. Juby, T.J. King & Hippocrateaceae). In: Flora Zambesiaca S.W. Tarn. 1963. Pristimerin. Part IV. II/2: 355-418. Crown Agents for Over­ Total structure. J. Chem. Soc. Part III. seas Governments and Administrations, 1963: 2884-2889. London.

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Roth,1. 1973. Estructura anatomica de la cor­ Van Wyk, A.E. 1985. The genus Eugenia teza de algunas especies arboreas venezo­ (Myrtaceae) in southern Africa: structure lanas de Celastraceae. Acta Bot. Venez. 7: and taxonomic value of bark. S. Afr. J. 83-100. Bot. 51: 157-180. Roth, I. 1981. Structural patterns of tropical Weber, W. 1913. Beiträge zur vergleichen­ barks. Handbuch der Pflanzenanatomie. den Anatomie der Wurzeln einiger Fami­ IX/3. Gebr. Borntraeger, Berlin. lien der Sapindales mit Rücksicht auf die Schlechter, M.S. & H.L. Haller. 1942. Iden­ Systematik. Ph.D. Thesis. Univ. Gottin­ tity of the red pigment in the roots of gen. Tripterygium wilfordii and Celastrus Whitmore, T. C. 1962a. Studies in systematic scandens. J. Am. Chem. Soc. 64: 182- bark morphology. 1. Bark taxonomy in 183. Dipterocarpaceae. New Phytol. 61: 191- Solereder, H. 1908. Systematic anatomy of 207. the dicotyledons. 1& 11. Clarendon Press, Whitmore, T.C. 1962b. Studies in systematic Oxford. bark morphology. III. Bark taxonomy in Thorenaar, A. 1926. Onderzoek naar bruik­ Dipterocarpaceae. Gdns' Bull., Singapore bare kenmerken ter identificatie van boo­ 19: 321-371. men naar hun bast. Meded. Proefstation Zahur, M.S. 1959. Comparative study of sec­ Boschwezen, Batavia 16: 1-207 & Atlas. ondary phloem of 423 species of woody Trockenbrodt, M. 1990. Survey and discus­ dicotyledons belonging to 85 families. sion of the terminology used in bark anat­ Mem. Cornell Univ. Agric. Exp. Stn 358: omy. IAWA Bull. n.s. 11: 141-166. 1-160.

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