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IAWA Journal, Vol. 22 (3), 2001: 301–330

WOOD ANATOMY OF SCHEFFLERA AND RELATED TAXA

(ARALIACEAE). II. SYSTEMATIC WOOD ANATOMY OF

NEW CALEDONIAN SCHEFFLERA by Alexei A. Oskolski1 & Porter P. Lowry II2a & b

SUMMARY

The wood anatomy of 22 of the 26 species of Schefflera occurring in New Caledonia was studied. Only two features (the presence of scalariform perforation plates and scanty paratracheal axial parenchyma) appear to be constant throughout the species examined. The pattern of wood structure diversity was analyzed using PCA; the results generally agree with the current recognition of four groups of species among New Caledonian Schefflera based on macromorphology. Three of these groups (Dizygotheca, “Canacoschefflera” and “Gabriellae”) represent natural assemblages closely related to one another. The fourth group (Schefflera sect. Schefflera) is isolated from the others, as indicated by its very large rays and abundant septate fibres. The occurrence of crystals in chambered cells of axial parenchyma was observed for the first time in Araliaceae. The wood structure of Schefflera plerandroides, previously placed in the segregate genus Octotheca, shows no essential differences from that of the other members of the Dizygotheca group, supporting the hypothesis that polymerous flowers have evolved independently at least twice within the Schefflera alliance. Key words: Araliaceae, Schefflera, Dizygotheca, Canacoschefflera, New Caledonia, systematic wood anatomy, crystals, chambered cells.

INTRODUCTION

Schefflera J.R. Forst. & G. Forst. is the largest genus of Araliaceae, with an estimated number of species ranging from 400 (Grushvitzky et al. 1985) to 650–700 (Lowry 1989), or as high as 900 (Frodin 1995), and making up more than half of the family. Schefflera is currently circumscribed broadly (Frodin 1975, 1982, 1989, 1993; see also Lowry 1989) to include several segregates usually recognized as synonyms (e.g., Agalma, Brassaia, Cephaloschefflera, Crepinella, Geopanax, Heptapleurum, Neocus- sonia, Scheffleropsis, and Sciadophyllum), plus several others that have been main-

1) Botanical Museum, V.L. Komarov Botanical Institute of the Russian Academy of Sciences, Prof. Popov str. 2, 197376 St. Petersburg, Russia [E-mail: [email protected]]. 2a) Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63166-0299, U.S.A. [E-mail: [email protected]]. 2b) Laboratoire de Phanérogamie, Muséum National dʼHistoire Naturelle, 16 rue Buffon, 75005 Paris, France [E-mail: [email protected]].

Downloaded from Brill.com10/09/2021 01:50:26AM via free access 302 IAWA Journal, Vol. 22 (3), 2001 Oskolski & Lowry II — Wood anatomy of Schefflera 303 tained as distinct in some treatments (e.g., Didymopanax, Dizygotheca, Octotheca, and Plerandra). This broad interpretation of Schefflera has, however, been called into question in a recent study (Wen et al. 2001) in which molecular data suggest that the genus, as currently defined, may be polyphyletic. Species of Schefflera (sensu lato) occur in most tropical and subtropical regions, with especially high concentrations in Malesia, Southeast Asia, New Caledonia, the Andes and the Guyana Highlands. Among these areas, the small southwest Pacific island of New Caledonia (c. 17,000 km2) is remarkable because of its high levels of diversity and endemism, both within Schefflera (26 species) and among Araliaceae as a whole, with a total of eight genera and over 90 native species recorded, only two of which occur elsewhere (Lowry 1986b, 1989, unpubl. data; Lowry et al. 1986). The New Caledonian Schefflera species, along with a few close relatives on neighboring islands (cf. Smith 1985; Lowry 1989), also appear to be rather isolated systematically and their relationships to other groups in the genus are somewhat obscure. The diversity and distinctiveness of the New Caledonian flora in general, and of its Araliaceae in particular, are due in large part to the wide variety of habitat types present on the island, which result from the complex interactions of topography, cli- mate, and a special set of edaphic features, including large areas of ultramafic soils (cf. Morat 1993; Lowry 1998). This is compounded by the islandʼs long geological history, during which it has been isolated from Australia for approximately 80 million years (Kroenke 1996), serving as a refuge for many “primitive” vascular plants (Raven & Axelrod 1972, 1974; Raven 1980), including representatives of some basal line- ages of Araliaceae (Plunkett & Lowry 2001). All 26 species of New Caledonian Schefflera are endemic to the island (Lowry, unpubl. data). Their habit varies from small monocaulous treelets to large, well branched trees up to 20 m in height. Species occur primarily in moist evergreen forests; the genus is less well represented in sclerophyllous forests and maquis vegetation (cf. Jaffré et al. 1993; Lowry 1998). Four well-defined groups can be distinguished within the genus in New Caledonia based on morphological differences in the leaves, inflorescences, flowers, and fruits, as follows:

1) Schefflera sect. Schefflera is represented by three species in New Caledonia, with five additional members occurring in other island groups of the southwest Pacific (one species each in Vanuatu, Samoa, and New Zealand, and two species in Fiji; Lowry 1989). The type of the genus (S. digitata J.R. Forst. & G. Forst.) from New Zealand belongs to this section, which could thus be interpreted as “Schefflera in the strictest sense” (Lowry 1989). This group is distinguished by its paniculate inflorescences bearing numerous umbellules or racemules of small flowers with 5 stamens and an equal number of carpels and free styles, and its thin, often mem- branaceous leaves and almost succulent stems and petioles. 2) The Dizygotheca group, previously recognized as a distinct genus Dizygotheca N.E. Brown (including Octotheca R. Vig.) by several authors (e.g., Guillaumin 1948; Hutchinson 1967), has twelve species in New Caledonia (all endemic) and two additional representatives in Vanuatu (Lowry 1989). Members of this group are characterized by anthers with 8 thecae (vs. 4 thecae in all other Schefflera) and

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a distinctive paniculate-umbellate inflorescence structure in which the lateral axes usually have a median pseudo-whorl of umbellules (cf. Lowry 1989). They also have a chromosome number of n = 24 (as compared to n = 12 for nearly all other Schefflera examined to date) (Lowry 1986b, unpubl. data). Most Dizygotheca in New Caledonia have free styles (united in two species), and a majority are found on non-ultramafic substrates. Octotheca was originally described as a monotypic genus on the basis of its polymerous flowers (Viguier 1906; see also Viguier 1909, 1925; Hutchinson 1967; Eyde & Tseng 1971; Tseng & Hoo 1982) with 10–15 carpels and 10, 15 or 20 stamens (vs. 5–10 carpels and 5 stamens in Dizygotheca), but it otherwise shares all of the features that characterize the group, and should probably not be retained. 3) The “Canacoschefflera” group is an informally recognized assemblage of nine endemic species distinguished by their once- or twice-umbellate inflorescences bearing 2–5-carpellate flowers with an equal number of free or basally united styles, and leaves that are usually quite coriaceous. Species of “Canacoschefflera” occur primarily on ultramafic substrates at higher elevations. 4) The “Gabriellae” group is represented by two species in New Caledonia, and two others occurring elsewhere in the southwest Pacific,S. vanuatua Lowry in Vanuatu (Lowry 1989) and S. seemanniana A.C. Smith in Fiji (Smith 1985). Members of this group are characterized by strictly compound umbellate inflorescences bearing generally 5-merous flowers with the styles fused into a short beak, and leaflets with numerous parallel secondary veins. The New Caledonian species are often large trees that can play an important role in the composition of forest communi- ties, with one (S. gabriellae Baill.) occurring primarily on ultramafic substrates and the other (S. pancheri Baill.) found almost exclusively on other soil types. Wood anatomy has been shown to be a useful tool for examining infrageneric relationships within both Schefflera (Oskolski 1995) and other groups of Araliaceae (Rodriguez 1957; Oskolski 1996, 2001; Oskolski et al. 1997; Oskolski & Lowry 2000). Oskolski (1995), using a representative sample of members of the genus from throughout the world, recognized seven broad groups within Schefflera on the basis of their wood structure, and proposed interpretations of their possible systematic relationships. However, data on the wood anatomy of New Caledonian Schefflera were scanty, and hence insufficient to formulate any conclusive interpretations about the position of the four groups represented on the island. In fact, only two (or perhaps three) of these species have been examined previously [S. gabriellae (Sarlin 1954; Oskolski 1994, 1995, 1996); S. elegantissima (Veitch ex Masters) Lowry & Frodin (Oskolski 1994, 1996 as Dizygotheca elegantissima), and Dizygotheca sp. (Record & Hess 1944; Metcalfe & Chalk 1950)].

The present study, which is part of a general survey of wood anatomy throughout Araliaceae (Oskolski 1994, 1995, 1996; Oskolski et al. 1997; Oskolski & Lowry 2000), surveys the wood structure of 22 of the 26 species of Schefflera represented in New Caledonia. The results are considered with regard to the systematic relationships among the groups and within the genus.

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Table 1. Variables selected for the Principal Component Analysis.

Variables Coding of the character states

1 radius of wood sample (mm) 2 average vessel element length (μm) 3 average tangential diameter of vessel lumina (μm) 4 percentage of solitary vessels 5 maximal number of vessel lumina per group 6 average vessel frequency per mm2 7 maximal bar number per perforation plate 8 level of specialization (sensu Bailey) of mostly scalariform = 0 intervessel pitting scalariform to opposite = 25 mostly opposite = 50 opposite to alternate = 75 mostly alternate = 100 9 average fibre length μ( m) 10 abundance of septate fibres no septate fibres = 0 solitary [up to c. 25% of fibres septate] = 25 common [c. 25–50% of fibres septate] = 50 predominate [c. 50–75% of fibres septate] = 75 almost all the fibres septate = 100 11 maximal ray width (number of cells) 12 average ray height (mm) 13 average number of uniseriate rays per mm 14 average number of multiseriate rays per mm 15 average annual rainfall (mm) 16 substrate type non-ultrabasic = 0 intermediate = 50 ultrabasic = 100

MATERIALS AND METHODS

The wood samples studied were collected in New Caledonia by the second author in the 1980s, and in 1997 by both authors and G.M. Plunkett (voucher specimens are deposited at LE, MO, NOU, P, and various other institutions). Several additional samples were obtained from institutional wood collections (Uw, Lw). The specimens were mostly taken from stems with a secondary xylem radius of more than 10 mm, although juvenile samples were studied in a few species. A list of the samples and their stem diameters is given in Tables 2–5. Standard procedures for the study of wood structure were employed to prepare sections and macerations for light microscopic studies (Carlquist 1988). Specimens for scanning microscopy were prepared according to Exley et al. (1974, 1977). De- scriptive terminology and measurements follow Carlquist (1988) and the IAWA List of Microscopic Features for Hardwood Identification (IAWA Committee 1989), ex-

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cept that for the diameter of intervessel pits the vertical dimension is recorded. Esti- mates of the average annual rainfall at the localities where the wood samples were collected are derived from the climatological map of New Caledonia (Section dʼHydro- logie de lʼORSTOM 1981). Principal Components Analysis (PCA) was used in an effort to differentiate among a) between-sample variation patterns of the wood anatomical characters examined and b) differences correlated with the habitats in which the plants grow. A total of 16 variables were selected for the PCA (Table 1). The wood samples of S. elegantissima [Uw UN911] and S. pancheri [Sarlin 302] were excluded from the numerical analysis because no data are available on their collection localities. The program package STATISTICA 5.0 was used to perform the PCA.

RESULTS

For the following descriptions, in cases where multiple samples of a species were examined and a feature was seen in only a portion of the material, the corresponding voucher collections are indicated in brackets.

Schefflera sect. Schefflera (Fig. 1–4, 25, 29, 30; Table 2)

Material studied: Schefflera candelabra Baill.: Plateau de Dogny, Lowry 4726. – S. pseudocandelabra R. Vig.: Plateau de Dogny, Lowry 3215; Mé Ori, Lowry 4795. – S. vieillardii Baill.: Mandjélia, Lowry 4747; Roches dʼOuaïème, Lowry 4786.

Diagnostic characters — Vessels narrow to moderately wide (up to 100 μm or more in diameter), perforation plates simple and scalariform, intervessel pitting exclusively scalariform, nearly all fibres septate, rays very high (commonly more than 2 mm) and wide (up to 8–12 cells), with 2–6 (up to 8) rows of upright and square marginal cells, multiseriate portions of rays distinctly wider than uniseriate ones, crystals not observed. Growth rings absent or indistinct, marked by tangential zones of thin-walled fibres. Vessels angular, rarely rounded in outline, rather small (tangential diameter usually less than 80 μm, up to 112 μm in S. pseudocandelabra [4795]). Vessel frequency from 20 per mm2 in S. pseudocandelabra [4795] to 54 per mm2 in S. candelabra. Vessels solitary or in radial multiples of 2–4 (up to 8 in S. candelabra). Vessel walls 3–6 μm thick. Tyloses not observed. Vessel element length (560–)870–1030(–1280) μm. Perforation plates simple and scalariform with few to numerous bars (up to 47), in highly or less oblique end walls. Intervessel pits exclusively scalariform, 4–7 μm in vertical size, with rounded margins and slit-like apertures. Vessel-ray and vessel- axial parenchyma pits half-bordered or with indistinct borders, similar to intervessel pits in size and shape. Helical thickenings absent. Vasicentric and vascular tracheids not observed. Fibres libriform, very thin- to thin-walled (fibre walls 2–6 μm thick), septate, with simple to minutely bordered pits with slit-like apertures in radial and tangential walls.

Downloaded from Brill.com10/09/2021 01:50:26AM via free access 306 IAWA Journal, Vol. 22 (3), 2001 Oskolski & Lowry II — Wood anatomy of Schefflera 307 16 0.91 0.90 0.57 0.54 0.70 Aver- 4: Average Average

maximum, 9:

the greatest /

15 -2.60 -1.87 -2.20 -1.85 -2.31

14 -0.67 -0.49 -2.24 -1.64 -1.12 Scores of Factor 2 —

15:

13 0.1 0.2 0.2 0.1 0.3

. 12 3.8 3.5 2.7 2.8 3.7

Radius of wood sample (mm) — Percentage of solitary vessels 11 3: Schefflera 6: 2.3/8.1 1.3/3.2 2.2/4.0 2.7/6.1 3.8/10.4 Scores of Factor 1 —

: Height of multiseriate rays (average

sect.

11 m) — 14: μ 10 5.4/8 5.1/8 6.6/10 7.4/12 6.9/10

Schefflera min.-max. number of bars per perforation plate — 9

non-ultrabasic) — 1185 1072 1045 1432 1260 = maximum,

Usual

8 8: 0/0-44 0/0-47 0/0-38 0/0-18 0/0-26

7 54 52 20 24 39 intermediate; – =

6 16/8 19/6 23/5 20/6 17/6 Number of uniseriate rays per mm —

13:

ultrabasic; ± = 5 67/92 61/88 58 /74 82/112 75/108

4 Vessel frequency (per sq.mm)Vessel — Tangential diameter Tangential of vessels (average 873 942 958 1032 1014 7: 5:

Width Width of multiseriate rays (average / maximum, cells) —

3 12 12 23 22 15 10: Table 2. Wood anatomical features of the species Wood 2. Table

m) — μ 2 – – – ± + Type of substrate (+ Type

m) — 2:

μ 1 1700 1700 1500 2000 2500

Number of multiseriate rays per mm — 12: Scores of Factor 3. (Lowry 4726) (Lowry 3215) (Lowry 4795) (Lowry 4747) (Lowry 4786) Annual rainfall (mm) — 1: age length of vessel elements ( number of vessels in a vessel group — length of libriform fibres ( mm) — 16: S. candelabra S. pseudocandelabra S. pseudocandelabra S. vieillardii S. vieillardii

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Legends on page 308.

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Axial parenchyma scanty paratracheal. Strands composed of 8–14 cells. Helical thickenings rarely present on inner walls of several axial parenchyma cells in S. candelabra [4726] (Fig. 4). Rays 2–4 per mm, uni- and multiseriate, mostly 3–8 cells in width (up to 12 in S. pseudocandelabra [4795]). Rays very high, commonly more than 2 mm (up to 10.4 mm in S. vieillardii [4786]). Multiseriate rays composed of procumbent body cells, and upright and square cells forming complete sheaths and 2–6 (up to 8) marginal rows (Kribsʼ type Heterogeneous I). Uniseriate rays composed of upright and square cells. Radial canals small (20–30 μm in diameter), bordered by few rather large thin-walled epthelial cells (Fig. 2). Crystals not observed.

The Dizygotheca group (Fig. 5–10, 22, 30, 35, 36; Table 3)

Material studied: Schefflera baillonii (R. Vig.) Lowry, ined.: Roches dʼOuaïème, Lowry 4782. – S. elegantissima (Veitch ex Masters) Lowry & Frodin: sine loc., Cantonpark 74-713, Uw UN911; Mt. Mou, Lowry 3801, 4715. – S. moratiana Lowry, ined.: Ponandou River valley, Lowry 4762, 4767. – S. nono Baill.: Plateau de Dogny, Lowry 4731. – S. osyana (Hort.) Lowry & Frodin, ined.: Plateau de Dogny, Lowry 4734. – S. plerandroides (R. Vig.) Lowry, ined.: Mandjélia, Lowry 4748, 4751; Roches dʼOuaïème, Lowry 4777, 4780. – S. polydactylis (Montrousier) Lowry, ined.: Mt. Poum, Lowry 3327; Mt. Taom, Lowry 3790. – S. reginae (Hort. Linden ex André) Lowry, ined.: Mt. des Sources, Lowry 3766; Mt. Dzumac, Lowry 4651, 4660; Mt. Humboldt, Plunkett 1483. – S. toto Baill.: Plateau de Dogny, Lowry 4727. – S. veitchii (Hort. ex Carrière) Frodin & Lowry: Baie Tina, Lowry 3390, 4665. – Schefflera sp.: New Caledonia, Pouembout, Lowry 4737.

Diagnostic characters — Vessels narrow (less than 90 μm in diameter), perforation plates almost exclusively scalariform, intervessel pitting mostly scalariform to opposite, septate fibres solitary to common, multiseriate rays with 1–4 (up to 10) rows of upright and square marginal cells, rays 6–10 per mm, multiseriate portions of rays relatively narrow (often twice as wide as their uniseriate portions), ray height commonly exceeding 0.8 mm, crystals present in upright and square ray cells in some species.

← Fig. 1–4. Species of Schefflera sect. Schefflera. — 1 & 2: Schefflera vieillardii (Lowry 4747); 1: TS, growth rings absent; 2: TLS, scalariform intervessel pitting, numerous septate fibres, large heterogeneous rays with small radial canals (arrows). – 3 & 4: S. candelabra (Lowry 4726); 3: TS, growth ring boundaries indistinctly marked by zones of thin-walled fibres; 4: TLS, axial parenchyma cells bearing helical thickenings on cell walls (arrows). — Scale bars = 100 μm; magnification of Fig. 1 & 2 as in Fig. 3. → Fig. 5–8. Species of the Dizygotheca group. — 5 & 6: Schefflera reginae (Lowry 3766); 5: TS, growth rings absent; 6: TLS, multiseriate portions of heterogeneous rays up to twice as wide as their uniseriate portions. – 7 & 8: S. veitchii (Lowry 4665); 7: TS, growth ring boundary in-distinctly marked by the vessel arrangement; 8: TLS, multiseriate portions of heterogeneous rays distinctly wider than uniseriate ones, radial canal, prismatic crystals in marginal ray cells (arrows). — Scale bar = 100 μm; magnification of Fig. 5–7 as in Fig. 8.

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maximum, 9:

the greatest /

15 0.15 0.22 -0.11 -0.19 -0.38 -0.33 -0.47 -0.38 -0.68

14 0.52 0.27 0.27 0.47 0.72 1.07 -0.65 -0.12 -1.04 Scores of Factor 2 —

15:

13 2.1 1.4 0.8 0.9 1.5 2.5 2.7 1.4 2.0 2.8

12 4.0 6.2 6.0 5.6 4.3 3.6 3.4 4.6 4.5 5.3

Radius of wood sample (mm) — Percentage of solitary vessels 11 3: 6: 0.6/1.3 0.6/1.3 0.5/1.2 0.5/0.8 0.8/1.6 0.5/0.8 0.6/0.8 0.7/1.0 0.5/0.8 0.4/0.6 Scores of Factor 1 — group. : Height of multiseriate rays (average

11 m) — 14: μ 10 2.5/4 2.9/4 2.3/3 2.8/4 4.4/6 2.2/3 3.2/5 3.6/5 2.9/4 3.4/5

min.-max. number of bars per perforation plate — 9

Dizygotheca /

843 non-ultrabasic) — 1194 1053 1389 1012 1259 1230 1063 1391 1007 = maximum,

Usual

8 8: maximum, cells) —

9/2-23 4/1-33 5/2-20 5/1-19 9/1-30 4/1-27 5/2-22 3/1-32 10/2-24 17/4-28

7 49 56 49 35 51 51 54 38 36 77 intermediate; – =

6 16/6 13/8 36/5 41/5 26/8 13/8 36/7 24/5 48/5 21/10 Number of uniseriate rays per mm —

13:

ultrabasic; ± = 5 48/64 60/77 62/81 55/88 47/60 54/72 44/68 68/88 53/80 46/60

4 Table 3. Wood of the Wood anatomical features 3. Table Vessel frequency (per sq.mm)Vessel — Tangential diameter Tangential of vessels (average 898 798 864 992 932 684 922 1119 1151 1061 7: 5:

Width of multiseriate rays (average

3 22 18 28 29 18 22 27 29 16 >50 10:

m) — μ 2 – – – – – – – – + Type of substrate (+ Type

m) — 2:

μ 1 2500 1700 1700 3000 3000 1700 1700 2000 2000

Number of multiseriate rays per mm — 12:

Scores of Factor 3. (Lowry 4782) (Uw UN911) (Lowry 3801) (Lowry 4715) (Lowry 4762) (Lowry 4767) (Lowry 4731) (Lowry 4734) (Lowry 4748) (Lowry 4751) Annual rainfall (mm) — 1: age length of vessel elements ( number of vessels in a vessel group — length of libriform fibres ( mm) — 16: S. baillonii S. elegantissima S. elegantissima S. elegantissima S. moratiana S. moratiana S. nono S. osyana S. plerandroides S. plerandroides

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15 0.10 0.22 0.15 -0.11 -0.06 -0.09 -0.15 -0.22 -0.43 -1.02 -0.58 -1.17

14 0.46 0.27 1.00 1.51 0.69 1.55 1.14 0.73 0.83 1.28 0.93 0.57

13 2.5 2.0 2.2 2.0 1.5 3.3 2.9 1.8 4.2 2.1 0.8 2.2

12 4.5 3.7 5.2 4.7 5.2 5.8 4.3 4.0 5.4 8.1 6.4 8.1

11 0.5/1.0 0.6/0.8 0.6/1.5 0.6/1.1 0.5/0.8 0.6/0.9 0.5/0.9 0.5/0.8 0.7/1.3 0.6/0.9 0.4/0.7 0.8/1.5

10 2.4/4 2.6/4 2.9/4 2.8/4 2.7/4 2.2/3 4.9/8 2.6/4 3.7/5 3.5/6 3.5/5 3.4/5

9 909 969 978 959 1117 1160 1168 1082 1047 1053 1016 1226

8 4/1-22 5/0-20 6/2-19 7/3-18 5/1-14 4/1-23 7/2-20 2/2-23 5/1-23 5/2-24 18/3-24 17/5-38

7 49 37 50 80 70 70 71 49 58 83 63 56

6 36/5 31/5 20/6 8/12 29/6 25/8 17/7 44/7 20/8 34/6 11/10 18/10

5 45/64 41/56 51/74 51/68 46/64 48/74 39/53 42/60 44/56 48/68 50/68 42/64

4 860 914 767 833 784 783 788 879 849 749 905 1029

3 8 11 11 39 19 21 16 19 16 33 15 16

2 – – – – – – + + + + +

1 2500 2500 1500 1500 4000 1700 1700 4000 1700 1000 1000 1000

sp. (Lowry 4777) (Lowry 4780) (Lowry 3327) (Lowry 3790) (Lowry 3766) (Lowry 4651) (Lowry 4660) (Plunkett 1483) (Lowry 4727) (Lowry 3390) (Lowry 4665) (Lowry 4737) reginae toto . . (Table 3 continued) (Table S. plerandroides S. plerandroides S. polydactylis S. polydactylis S. reginae S. reginae S. reginae S S S. veitchii S. veitchii Schefflera

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Growth rings absent or indistinctly marked by tangential zones of thin-walled fibres mixed with solitary strands of marginal parenchyma (S. moratiana [4767], S. nono, S. reginae [Plunkett 1483]), and also by zones of more numerous vessels (S. veitchii [4665]), or by lines of marginal parenchyma (S. polydactylis [3790], S. veitchii [3390]). Vessels rounded, rarely angular in outline, rather small (tangential diameter < 90 μm). Vessel frequency from 35 per mm2 in S. elegantissima [4715] to 83 per mm2 in S. veitchii [3390]. Vessels solitary and in radial multiples of 2–5 (up to 12 in S. polydactylis [3790]). Vessel walls 2–5 μm thick. Tyloses present in S. elegantissima [3801], S. osyana [4734], S. moratiana [4762], S. polydactylis [3790], S. reginae, S. veitchii [4665] and S. toto [4727], but not observed in other samples. Vessel element length (380–)680–1150(–1650) μm. Perforation plates scalariform with few to numerous bars (up to 38 in Schefflera sp. [4737]), reticulate, sometimes simple (in S. plerandroides [4780] only) in more or less oblique end walls. Intervessel pits scalariform to opposite (mostly opposite in S. elegantissima and S. osyana), sometimes alternate, 6–8(–9) μm in vertical diameter, with rounded margins and slit-like apertures. Ves- sel-ray and vessel-axial parenchyma pits simple or half-bordered with small borders, similar to intervessel pits in size and shape. Helical thickenings absent. Vasicentric and vascular tracheids not observed. Fibres libriform, mostly thick-walled (fibre walls 3–6(–8) μm) and occasionally thin-walled (especially in S. elegantissima), mostly non-septate (septate fibres relatively numerous in S. elegantissima, S. moratiana [4767], S. osyana, and few in other species, not observed in S. polydactylis [3327] and S. reginae [4660], located mostly in immediate vicinity of rays), with few simple to minutely bordered pits (large, distinctly bordered pits > 5 μm in diameter in S. reginae [3766] and S. toto [4727]), with slit-like apertures in radial walls. Axial parenchyma scanty paratracheal and marginal (forming continuous tangential lines in S. veitchii [3390], interrupted lines in S. polydactylis [3790], S. moratiana [4767], S. nono and S. reginae [Plunkett 1483]). Strands composed of (3–)4–6(–8) cells. Rays 6–10 per mm, uni- and multiseriate of 2–4 cells in width (up to 6 in S. moratiana [4762] and S. veitchii [4665], and to 8 in S. reginae [4660]). Ray height commonly less than 1 mm, but > 1 mm in S. elegantissima [3801; UN911], S. polydactylis, S. osyana [4734], S. toto [4727] and Schefflera sp. [4737], up to 1.5 mm high in S. moratiana [4762]. Multiseriate rays composed mostly of procumbent body cells (mixed occasionally with square and upright cells) and 1–4 (up to 10) marginal rows of square and upright cells (Kribsʼ type Heterogeneous I); solitary sheath cells rarely present. Multiseriate portions of rays usually a little wider than (up to twice as wide as) the uniseriate portions (except in S. elegantissima [4715], S. osyana [4734], S. moratiana [4762], S. plerandroides [4751], S. veitchii [4665], and Schefflera sp. [4737], with multiseriate portions of rays usually distinctly wider than uniseriate ones). Uniseriate rays composed mostly of square and upright cells. Radial canals present in S. polydactylis [3327] and S. veitchii, rather wide (30–50 μm in diameter), bordered by numerous small, thin-walled epithelial cells. Prismatic calcium oxalate crystals in upright and square cells of both multiseriate and uniseriate rays in S. elegantissima,

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S. osyana [4734], S. moratiana [4762], S. polydactylis [3790], S. veitchii, S. toto [4727], and Schefflera sp. [4737]. Crystal-containing cells evenly distributed among other ray cells. Note — The wood sample described by Oskolski (1994, 1995, 1996) under the name S. nono (SFCw s.n.) was undoubtedly misidentified. As no accompanying voucher specimen has been located, we cannot verify its identity, but it probably belongs to a species of Polyscias.

The “Canacoschefflera” group (Fig. 11–16, 21, 23, 26–28, 32–34; Table 4)

Material studied: Schefflera crassipes Baill.: Mt. Mou, Lowry 4701; Mé Ori, Lowry 4797. – S. elongata Baill.: Mt. Dzumac, Lowry 3353, 4659. – S. emiliana Baill.: Mt. Humboldt, Plunkett 1486a (coll. Suprin). – S. gordonii Lowry, ined.: Col de Yaté, Lowry 4674. – S. neocaledonica Lowry, ined.: Mt. Dzumac, Lowry 4656. – S. pachyphylla Harms: Upper Ouinné River Basin, Lowry 3691. – S. taomensis Lowry, ined.: Mt. Taom, Lowry 3769; Kopéto Massif, Lowry 4742. – S. veillonorum Lowry, ined.: Roches dʼOuaïème, Lowry 3917, 4774, 4784.

Diagnostic characters — Vessels narrow (diameter commonly less than 90 μm), perforation plates scalariform and simple, intervessel pitting mostly opposite to alternate, septate fibres solitary or absent, rays less than 6 per mm, height less than 0.7 mm, multiseriate rays composed of procumbent body cells or also of square and upright cells forming 1–2 (up to 4) marginal rows, crystals present in chambered cells of diffuse axial parenchyma in some species. Growth rings absent (S. pachyphylla) or indistinctly marked by tangential zones of thin-walled fibres S( . crassipes [4742]), by bands of thick-walled fibres S.( gordonii), or by interrupted lines of marginal parenchyma (S. elongata [3353]). Vessels rounded, rarely angular in outline, rather small (tangential diameter usually < 80 μm except in S. veillonorum [4784] up to 104 μm). Vessel frequency from 22 per mm2 in S. veillonorum [4774] to 72 per mm2 in S. taomensis (and to 142 per mm2 in juvenile wood of S. emiliana). Vessels solitary and in radial multiples of 2–5

→ Fig. 9–12. Species of the Dizygotheca and “Canacoschefflera” groups. — 9 & 10: Schefflera moratiana (Lowry 4767); 9: TS, growth ring boundaries (arrows) indistinctly marked by zones of thin-walled fibres mixed with solitary strands of marginal parenchyma; 10: TLS, solitary septate fibres (arrow), multiseriate portions of heterogeneous rays up to twice as wide as their uniseriate portions. – 11 & 12: S. elongata (Lowry 4659); 11: TS, growth rings absent, solitary strands of diffuse axial parenchyma (arrows); 12: TLS, prismatic crystals in axial parenchyma cells, homogeneous rays. — Scale bar = 100 μm; magnification of Fig. 9, 10 & 12 as in Fig. 11. →→ Fig. 13–16. Species of the “Canacoschefflera” group. — 13 & 14: Schefflera veillonorum (Lowry 4774); 13: TS, growth rings absent, no diffuse axial parenchyma; 14: TLS, homogeneous rays. – 15 & 16: S. crassipes (Lowry 4742); 15: TS, growth ring boundary (arrow) indistinctly marked by zone of thin-walled fibres; 16: TLS, heterogeneous rays with 1 or 2 marginal rows of square and upright cells. — Scale bar = 100 μm; magnification of Fig. 13, 14 & 16 as in Fig. 15.

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Legends on page 313.

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Legends on page 313.

Downloaded from Brill.com10/09/2021 01:50:26AM via free access 316 IAWA Journal, Vol. 22 (3), 2001 Oskolski & Lowry II — Wood anatomy of Schefflera 317 16 0.34 0.36 1.12 2.36 0.77 0.88 0.68 0.73 1.98 0.33 0.23 Aver- -0.13 -0.31 4: Average Average

maximum, 9:

the greatest /

15 0.46 1.02 0.73 0.58 0.21 0.81 1.18 1.05 0.36 0.78 0.96 1.09 0.86

14 0.17 0.27 2.05 0.22 0.32 0.57 0.21 -0.33 -0.03 -0.22 -0.37 -0.35 -0.39 Scores of Factor 2 —

15:

13 2.0 0.8 1.1 1.2 2.8 1.0 1.7 0.5 1.1 0.9 0.9 0.4 0.6

12 3.7 3.2 3.4 3.5 2.9 1.5 2.9 2.0 3.0 2.1 2.8 2.2 2.7

Radius of wood sample (mm) — Percentage of solitary vessels 11 3: 6: 0.3/0.5 0.3/0.5 0.3/0.5 0.2/0.4 0.5/0.9 0.3/0.5 0.2/0.4 0.4/0.7 0.3/0.6 0.4/0.5 0.3/0.5 0.3/0.5 0.3/0.4 Scores of Factor 1 — ” species. : Height of multiseriate rays (average

11 m) — 14: μ 10 2.5/4 2.7/4 2.8/4 2.2/4 2.7/5 2.3/3 2.2/3 2.8/4 2.1/3 2.2/3 3.0/4 2.6/4 3.3/5

min.-max. number of bars per perforation plate — 9

882 980 930 979 non-ultrabasic) — 1126 1167 1142 1035 1044 1276 1015 1220 1000 = maximum,

Canacoschefflera Usual

8 8: maximum, cells) —

6/0-24 1/0-17 1/0-27 5/0-18 3/0-19 5/0-22 4/1-30 5/0-21 4/0-20 6/0-17 2/0-11 4/2-18 5/0-22

7 32 31 32 39 34 35 32 72 41 27 22 26 intermediate; – 108 =

6 6/9 12/6 7/17 19/8 20/7 21/6 30/5 15/7 11/7 27/7 10/11 21/10 17/19 Number of uniseriate rays per mm —

13:

ultrabasic; ± = 5 64/84 55/77 57/72 40/60 53/68 59/84 51/71 52/71 59/80 48/71 53/72 66/92 72/104

4 Vessel frequency (per sq.mm)Vessel — Tangential diameter Tangential of vessels (average 850 906 738 920 722 857 921 847 938 884 909 802 1080 7: 5: Table 4. Wood Wood anatomical features of “ 4. Table Width Width of multiseriate rays (average

3 23 27 19 20 10 27 29 19 12 24 17 23 27 10:

m) — μ 2 – – – + + + + + + + + + Type of substrate (+ Type

m) — 2:

μ 1 1700 1500 1700 1700 4000 3000 1700 3000 1300 1500 2500 2500 2500

Number of multiseriate rays per mm — 12: Scores of Factor 3. (Lowry 4701) (Lowry 4797) (Lowry 3353) (Lowry 4659) (Plunkett 1486a) (Lowry 4674) (Lowry 4656) (Lowry 3691) (Lowry 3769) (Lowry 4742) (Lowry 3917) (Lowry 4774) (Lowry 4784) Annual rainfall (mm) — 1: age length of vessel elements ( number of vessels in a vessel group — length of libriform fibres ( mm) — 16: S. crassipes S. crassipes S. elongata S. elongata S. emiliana S. gordonii S. neocaledonica S. pachyphylla S. taomensis S. taomensis S. veillonorum S. veillonorum S. veillonorum

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(up to 19 in S. crassipes [4742]). Vessel walls (2–)4–6(–10) μm thick. Tyloses not observed. Vessel element length (390–)740–1080(–1510) μm. Perforation plates scalariform with few to numerous bars (up to 27 in S. elongata [4659]), reticulate and simple (not observed in S. crassipes [4701, 4797]), in more or less oblique end walls. Intervessel pits opposite and transitional to scalariform (in S. elongata [3353], S. emiliana, S. gordonii, S. pachyphylla, S. taomensis), and alternate; rather small (4–8 μm in vertical diameter) in S. crassipes [4701], S. elongata and S. veillonorum [4774], and larger (7–10 μm in vertical diameter) in other species, rounded and oval, with slit-like apertures. Vessel-ray and vessel-axial parenchyma pits simple and half-bordered with small borders, similar to intervessel pits in size and shape. Helical thickenings absent. Vasicentric and vascular tracheids not observed. Fibres libriform, mostly thick-walled ((2–)5–10(–14) μm), mostly non-septate (septate fibres rarely present in S. crassipes [4701], S. elongata, S. emiliana, S. gordonii, S. taomensis [4742], and also in S. veillonorum [4784], where they are located mostly in the immediate vicinity of rays), with few simple to minutely bordered pits with slit-like apertures in radial walls. Axial parenchyma scanty paratracheal in solitary strands near vessels, and also diffuse in solitary strands (commonly containing crystal-bearing chambered cells) located in immediate vicinity of rays in S. crassipes, S. elongata, S. emiliana, and marginal in tangential interrupted lines in S. elongata [3353]. Strands composed of (3–)4–7(–10) cells. Rays 2–6 per mm, uni- and multiseriate of 2–5 cells in width (2–3 in S. crassipes, S. gordonii, S. neocaledonica, S. taomensis [4742], and 2–5 in S. emiliana and S. veillonorum [4784]). Ray height less than 0.7 mm (up to 0.9 mm in juvenile wood of S. emiliana). Multiseriate rays composed of procumbent body cells (Kribsʼ type Ho- mogeneous I predominant in S. crassipes [4701] and S. veillonorum) or also of square and upright cells forming 1–2 marginal rows (up to 4 in S. elongata and S. taomensis) (Kribsʼ type Heterogeneous IIb predominating in other species); solitary sheath cells rarely present in S. elongata and S. pachyphylla, absent in other species. Multi- seriate portions of rays usually distinctly wider than uniseriate portions. Uniseriate rays composed of square and upright as well as procumbent cells. Radial canals not observed. Crystals not found in ray cells. Prismatic calcium oxalate crystals present in chambered (rarely non-chambered) cells of diffuse parenchyma in S. crassipes, S. elongata and S. emiliana, and also in septate fibres inS. elongata, not observed in ray cells.

→ Fig. 17–20. Species of the “Gabriellae” group. — 17 & 18: Scheffelra pancheri (Lowry 4661); 17: TS, growth ring boundary indistinctly marked by zone of relatively thin-walled fibres mixed with solitary strands (arrows) of marginal axial parenchyma; 18: TLS, mainly homogeneous rays. – 19 & 20: S. gabriellae (Lowry 3297); 19: TS, growth rings absent; 20: TLS, heterogeneous rays with 1 or 2 marginal rows of square and upright cells, radial secretory canals (arrows). — Scale bar = 100 μm; magnification of Fig. 17, 18 & 20 as in Fig. 19.

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Legends on page 317.

Downloaded from Brill.com10/09/2021 01:50:26AM via free access 318 IAWA Journal, Vol. 22 (3), 2001 Oskolski & Lowry II — Wood anatomy of Schefflera 319 16 2.02 Aver- -0.39 -0.61 -0.80 -0.31 -0.80 4: Average Average

maximum, 9:

the greatest /

15 0.92 0.77 1.28 1.16 0.83 1.29

14 -1.27 -0.74 -2.20 -1.63 -0.97 -1.61 Scores of Factor 2 —

15:

13 0.4 0.5 0.2 0.3 0.3 0.3 0.6

12 2.6 3.6 2.2 2.8 3.2 2.4 2.5

Radius of wood sample (mm) — Percentage of solitary vessels 11 3: 6: 0.3/0.4 0.3/0.5 0.4/0.7 0.4/0.6 0.3/0.4 0.4/0.7 0.5/0.8 Scores of Factor 1 — : Height of multiseriate rays (average

” species.

11 m) — 14: μ 10 3.8/6 3.4/5 2.8/4 3.5/5 3.4/6 4.1/6 3.3/5

min.-max. number of bars per perforation plate — Gabriellae 9

non-ultrabasic) — 1179 1249 1025 1278 1344 1469 1406 = maximum,

Usual

8 8: maximum, cells) —

3/0-14 5/0-30 7/1-30 2/0-26 4/1-33 3/0-16 2/0-24

7 26 27 20 18 17 18 40 intermediate; – =

6 21/6 24/5 33/4 28/4 30/7 22/5 7/16 Number of uniseriate rays per mm —

13:

ultrabasic; ± = 5 65 /84 82/112 87/116 76/100 66/100 96/149 80/100

4 864 913 Vessel frequency (per sq.mm)Vessel — Tangential diameter Tangential of vessels (average 1116 Table 5. Wood Wood anatomical 5. features Table of the “ 1129 1235 1272 1083 7: 5:

Width Width of multiseriate rays (average

3 28 38 45 >50 >30 >50 >40 10:

m) — μ 2 – – – + + + Type of substrate (+ Type

m) — 2:

μ 1 1300 1700 3000 2000 1700 1700

Number of multiseriate rays per mm — 12: Scores of Factor 3. (Lowry 3297) (Lowry 4648) (Lowry 4681) (Lowry 4755) (Sarlin 302) (Lowry 4661) (Lowry 4721) Annual rainfall (mm) — gabriellae

1: age length of vessel elements ( number of vessels in a vessel group — length of libriform fibres ( mm) — 16: S. gabriellae S. gabriellae S. gabriellae S. S. pancheri S. pancheri S. pancheri

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The “Gabriellae” group (Fig. 17–20, 24; Table 5)

Material studied: Schefflera gabriellae Baill.: Ile des Pins, Lowry 3297; Mt. Dzumac, Lowry 4648; Col de Yaté, Lowry 4681; Mandjélia, Lowry 4755. – S. pancheri Baill.: Mt. Dzumac, Lowry 4661; Plateau de Dogny, Lowry 4721; sine loc., Sarlin 302; sine loc., Lw s.n. (ex CTFTw 6200, identified asS. andreana Baill.).

Diagnostic characters — Vessels wide (diameter often exceeding 90 μm), perforation plates scalariform and simple, intervessel pitting mostly opposite to alternate, septate fibres absent, multiseriate rays composed of procumbent body cells only, or with 1–2 marginal rows of upright and square cells, rays less than 4 per mm, less than 0.8 mm high, crystals rarely present in non-chambered cells of marginal axial parenchyma. Growth rings indistinctly marked by tangential zones of relatively thin-walled fibres and interrupted marginal rows of axial parenchyma, and by somewhat smaller vessels in S. pancheri [4661], absent in other samples. Vessels rounded, rarely angular in outline, rather wide (average tangential diameter > 65 μm, up to 116 μm in S. gabriellae [4648]), not numerous (vessel frequency from 17 per mm2 in S. gabriellae [4755] to 40 per mm2 in S. pancheri [4661]). Vessels mostly in radial multiples of 2–3 (up to 16 in S. pancheri [4661]) mixed with solitary ones. Vessel walls 2–6 μm (to 10 μm) thick. Tyloses noted in both S. gabriellae [4648, 4755] and S. pancheri [4661]. Vessel element length (640–)860–1270(–1720) μm. Perforation plates scalariform with few to numerous bars (up to 33 in S. pancheri [Sarlin 302]) or simple (exclusively scalariform in S. pancheri [Sarlin 302] and S. gabriellae [4681]), and reticulate, in more or less oblique end walls. Intervessel pits mostly alternate, rarely transitional to scalariform and opposite, 5–8 μm in vertical diameter, rounded and angular (mostly rounded in S. pancheri [Sarlin 302]), with slit- like and lens-like apertures. Vessel-ray and vessel-axial parenchyma pits half-bordered or with indistinct borders, scalariform to oval and rounded in outline, similar to intervessel pits in size, with lens-like, oval, or slit-like apertures. Unilaterally-compound pits not observed. Helical thickenings absent. Vasicentric and vascular tracheids not observed. Fibres libriform, thin- to thick-walled ((3–)5–7(–12) μm thick, up to 15 μm thick in S. pancheri [4661]), all non-septate, with simple to minutely bordered pits with slit-like apertures in radial walls. Axial parenchyma scanty paratracheal or narrowly vasicentric in solitary strands and incomplete sheaths. Uniseriate marginal rows of axial parenchyma also present in S. pancheri [4661]. Strands composed of (3–)4–8(–10) cells. Non-chambered (rarely

Fig. 21–24. Calcium oxalate crystals in cells of axial and ray parenchyma. — 21: Schefflera elongata (Lowry 4659). RLS, crystaliferous strands of diffuse axial parenchyma. – 22: S. elegantissima (Lowry 3801). RLS, heterogeneous rays with prismatic crystals in upright and square marginal cells. – 23: S. elongata (Lowry 4659). RLS, prismatic crystals in chambered axial parenchyma cells. – 24: S. pancheri (Lowry 4661). RLS, prismatic crystals in chambered cell of marginal axial parenchyma. — Scale bar = 100 μm; magnification of Fig. 21 as in Fig. 22; that of Fig. 23 as in Fig. 24.

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Fig. 25–29. Perforation plates, SEM. — 25: Schefflera vieillardii (Lowry 4747). Scalariform perforation plate with numerous bars. – 26–28. S. neocaledonica (Lowry 4656); 26: Reticulate perforation plate; 27: Scalariform perforation plate with numerous bars; 28: Perforation plates with few bars. – 29: S. vieillardii (Lowry 4747). Simple perforation plate. — Scale bars of Fig. 25–27 = 10 μm; of Fig. 28 & 29 = 100 μm.

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composed of both upright and procumbent cells. Radial canals present in S. gabriellae [3297] and S. pancheri [4721, Sarlin 302], bordered by numerous small, thin-walled epithelial cells. Crystals not observed.

Fig. 30–32. Intervessel pitting, SEM. – 30: Schefflera vieillardii (Lowry 4747). Scalariform pitting. – 31: S. elegantissima (Lowry 4715). Transitional pitting. – 32. S. neocaledonica (Lowry 4656). Alternate pitting. — Fig. 33 & 34: S. elongata (Lowry 4659). SEM, prismatic crystals in chambered axial parenchyma cells. — Fig. 35 & 36: S. elegantissima (Lowry 4715). SEM, prismatic crystals in ray cells. — Scale bars = 10 μm; magnification of Fig. 35 as in Fig. 36.

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NUMERICAL ANALYSIS

The loadings of the five factors with the greatest influence in the Principal Compo- nents Analysis (PCA) are shown in Table 6. Together they explain 79.3% of the total variation, with the first three alone accounting for more than 60% of the variation. The scores of the three most important factors are given for each of the four groups of New Caledonian Schefflera in Tables 2–5. The pattern of within-sample variation of wood characters and of the environmental variables examined (summarized by the distribution of the scores of Factors 1 and 2) is presented in Figure 37. Two well- delimited clusters can clearly be seen. The samples from Schefflera sect. Schefflera are completely separated from all others along the axis of Factor 2, with the remain- ing samples forming a broad cluster stretching across the axis of Factor 1. Within this second cluster, comprising the members of Dizygotheca and the “Canacoschefflera” and “Gabriellae” groups, three non-overlapping but essentially contiguous sub-clusters can be recognized, each corresponding to one of the species assemblages. In the projection of sample variation against Factors 1 and 3, however, no clearly delimited clusters can be seen, although the four taxonomic groups under study can be recognized as sub-clusters with only limited overlap.

“Canacoschefflera” “Gabriellae” Dizygotheca sect. Schefflera

Fig. 37. Pattern of within-sample variation of wood characters and of environmental variables for New Caledonian Schefflera species (summarized by the distribution of the scores of Factors 1 and 2 from the Principal Components Analysis).

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Table 6. The loadings of the five factors with the greatest influence in the Principal Components Analysis.

Factors Variance Variables Factor % loadings

1. 27.4 average length of vessel elements -0.70 average length of fibres -0.77 average diameter of vessel lumina -0.87 average vessel frequency per mm2 0.78 average number of uniseriate rays per mm 0.74

2. 22.8 level of the intervessel pitting specialization 0.85 (sensu Bailey) abundance of septate fibres -0.85 maximal width of rays -0.72 average height of rays -0.77

3. 12.7 percentage of solitary vessels -0.85 maximal number of vessels per group 0.71

4. 9.0 no significant correlations with any of the characters examined

5. 7.4 annual rainfall 0.71

DISCUSSION

The New Caledonian species of Schefflera show a considerable range in diversity in their wood structure: only two features, the presence of scalariform perforation plates and of scanty paratracheal axial parenchyma, appear to be constant throughout the taxa examined. These characters are also typical for a number of other Schefflera species studied from various parts of the world, including South China, Indo-China, Australia, New Zealand, Fiji, South America, and East Africa (Oskolski 1995). The pattern of wood structure diversity within the taxa studied generally agrees with the recognition of four species groups among New Caledonian Schefflera based on macromorphology. Results of the Principal Component Analysis suggest that Di- zygotheca, “Canacoschefflera” and “Gabriellae” represent natural assemblages, and further indicate that they are closely related to one another. The PCA also suggests a more isolated position for Schefflera sect. Schefflera, which likewise comprises a natural group. The members of “Canacoschefflera” are similar to those of “Gabriellae” in their overall wood anatomy, suggesting a close relationship. “Canacoschefflera” can, however, be distinguished by having smaller vessels (less than 90 μm in tangential diameter) that are more numerous (usually more than 30 per mm2), and also by more numerous rays (up to 6 per mm) and the presence of solitary septate fibres.

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The occurrence of crystals in chambered cells of axial parenchyma, observed here for the first time in Araliaceae in three species belonging to the “Canacoschefflera” group (S. crassipes, S. elongata (Fig. 21 & 22) and S. emiliana), and also in one sample of S. pancheri [4661] in the “Gabriellae” group (Fig. 24), could be regarded as additional evidence of a close relationship between these taxa. It should be noted that diffuse axial parenchyma (Fig. 11) is a rather uncommon wood character for Araliaceae. Besides its presence in Schefflera, this feature has also been recorded in the members of two well defined groups centered in New Caledonia and Australasia, one comprising Myodocarpus, Delarbrea, and Pseudosciadium (Oskolski et al. 1997), the other with Apiopetalum and Mackinlaya (Oskolski & Lowry 2000), each of which appears to represent a basally branching lineage within the order Apiales (= Araliaceae and Apiaceae) (Plunkett & Lowry 2001). The occurrence of crystalliferous chambered cells in the axial parenchyma of Araliaceae could be of value for clarifying relationships between this family and its apparent allies. Recent molecular evidence has clearly established a close relationship between Apiales and Pittosporaceae (Chase et al. 1993; Plunkett 1994; Plunkett et al. 1996, 1997), as suggested earlier on the basis of vegetative anatomy (Van Tieghem 1884), floral morphology (Jurica 1922) and base chromosome number and chemo- taxonomy (Jay 1969; Hegnauer 1971), and formalized in Dahlgrenʼs (1980) classification system. However, on the basis of wood anatomy, Carlquist (1981) questioned such a relationship, primarily because of the apparent absence of axial parenchyma bearing crystals in chambered cells in both Araliaceae and Apiaceae. The occurrence of this feature in several species of Schefflera appears, however, to refute Carlquistʼs interpretation. While our data do not suggest a direct relationship between Schefflera and Pittosporaceae, they do show that this feature occurs in Apiales and that it would be worth examining other members of the order for its presence. Based on wood anatomy, members of Dizygotheca appear to be rather close to those of the “Canacoschefflera” group (Fig. 37). They can, however, be separated by a number of features: the former have somewhat narrower and more numerous vessels, almost exclusively scalariform perforation plates, a predominance of scalariform intervessel pitting, more abundant septate fibres, more numerous rays (6–10 per mm as compared with 3–6 per mm in “Canacoschefflera”) with 1–4 (up to 10) rows of upright and square marginal cells Kribsʼ type Heterogeneous I (vs. 1–2 (up to 4) marginal rows in “Canacoschefflera”), a peculiar shape of the multiseriate rays (with the multiseriate portions of most rays as wide as the uniseriate ones), and also the distribution of crystals (contained in ray cells and never in axial parenchyma). Most of these distinctions are quantitative and vary more or less continuously; a sharp boundary between the two assemblages can only be seen in two characters, i.e., the type and morphology of rays. The wood structure of members of Dizygotheca appears to be less advanced (sensu Bailey) than in species of “Canacoschefflera” and “Gabriellae”, as indicated by their almost exclusively scalariform perforation plates and a predominance of scalariform intervessel pitting. Our data are consistent with Lowryʼs (1989) suggestion that Dizygotheca is close to “Canacoschefflera”, and that the latter is in turn related to “Gabriellae”.

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The wood structure of Schefflera plerandroides, previously placed in the segregate genus Octotheca (Viguier 1906; Hutchinson 1967), shows no essential differences from that of other members of the Dizygotheca group examined. Wood anatomy thus supports the hypothesis that polymerous flowers have evolved independently at least twice within the Schefflera alliance, once in the Dizygotheca group (i.e., in S. plerandroides) and a second time in the species traditionally referred to Tupidanthus and Scheffleropsis (now included by most authors in Schefflera; cf. Frodin 1975; Lowry et al. 1989), which appear on the basis of wood structure to be closely related to Schefflera subsections Octophyllae and Heptapleurum (Oskolski 1994, 1995, 1996). The interpretation of an independent origin of polymery is further supported by recent molecular data (Wen et al. 2001), which suggest a close relationship between Tupidanthus and several other Asian species assigned to Schefflera, but indicate the placement of the Dizygotheca group in a separate clade comprising largely Pacific taxa in several genera. Comparing the results obtained here with the general classification scheme of Schefflera based on wood anatomy proposed by Oskolski (1995), the members of the “Canacoschefflera” and “Gabriellae” groups can clearly be referred to the previously recognized Group D, which also includes taxa from Africa and America. Two subdivisions were initially proposed (D1 and D2) primarily on the basis of their ray types (Kribsʼ type Homogeneous I and Heterogeneous IIb respectively), but their validity now appears less reliable in the light of recent studies of a larger set of samples from Africa and South America (Oskolski & Lowry, in prep.). The position of members of “Canacoschefflera” and “Gabriellae” within Group D is, however, somewhat isolated, as indicated by such rather primitive (sensu Bailey) wood features as the presence of relatively long vessel elements and the occurrence of scalariform perforation plates with numerous (more than 10) bars, and also by small vessels (tangential diameter commonly less than 90 μm in “Canacoschefflera”), the scarcity or complete absence of septate fibres, and the tendency to form prismatic calcium oxalate crystals in the axial parenchyma cells. As for the members of Dizygotheca, they cannot be ascribed to any of the subdivisions proposed in Oskolskiʼs (1995) classification scheme, making it necessary to recognize a new Group E. The three New Caledonian species of Schefflera sect. Schefflera differ very distinctly from other members of the genus by their very large rays and abundant septate fibres, and are clearly referable to Group C2 of Oskolskiʼs (1995) classification scheme. Wood anatomical data thus confirm Lowryʼs (1989) suggestion of a close relationship between these species and the other members of the section studied to date. Specifically, the wood of the species in New Caledonia is more similar to that of the Fijian endemics S. vitiensis (A. Gray) Seem. and S. euthytricha A.C. Smith (which have a very primitive wood structure) than it is to the more highly specialized wood of S. digitata from New Zealand (Oskolski 1995). However, the New Caledonian species differ distinctly from other members of this group by the co-occurrence of both simple and scalariform perforation plates (the two Fijian species have almost exclusively scalariform perforation plates, whereas S. digitata is characterized by exclusively simple perforations), which represents an intermediate level of specialization of their wood structure.

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Helical thickenings were observed on the walls of a few axial parenchyma cells in S. candelabra (Fig. 4). This feature has been reported to occur very rarely in axial parenchyma of some representatives of Trigoniaceae (Heimsch 1942), Ancistrocladaceae (Gottwald & Parameswaran 1968), Chrysobalanaceae (Ter Welle 1975), Rubiaceae (Ohtani 1986), Rosaceae (H.G. Richter, pers. comm.), and Araliaceae, where it was found in a single sample of Mackinlaya macrosciadea (F. Muell.) F. Muell. (Oskolski & Lowry 2000). Although the presence of this character is of interest because of its rarity, it should be regarded as of questionable diagnostic value because of its spo- radic occurrence.

ACKNOWLEDGEMENTS

This research was supported by a stipend to the first author from the Deutscher Akademischer Aus- tauschdienst (DAAD) [the German Academic Exchange Service]. We wish to thank G.M. Plunkett for his collaboration in the field in New Caledonia and Australia, and P. Baas and B.J.H. ter Welle for their kind help in obtaining the wood samples from Lw and Uw. We are also grateful to P. Baas and an anonymous referee for valuable comments and suggestions on an earlier draft of the manuscript, and to the following persons: E.S. Chavchavadze, H.G. Richter, E. John, Ch. Waitkus, T. Potsch, J.-M. Veillon, Ph. Morat, B. Suprin, T. Jaffré, J. West, B. Hyland, B. Gray, and R. Jensen. Assistance was provided to the first author by the following: Ordinariat für Holzbiologie, Universität Hamburg; Bundesforschungsanstalt für Holz- und Forstwirtschaft, Hamburg; and the Botanical Museum, the V.L. Komarov Botanical Institute, St. Petersburg. The authors acknowledge courtesies extended in New Caledonia by the staffs of IRD-Nouméa, the Direction des Ressource Naturelles, Province Nord, and the Service Forêt, Bois et Environnement, Province Sud; and in Paris by the Muséum National dʼHistoire Naturelle. Field work was supported by a grant from the National Geographic Society (no. 5793-96 to G.M. Plunkett). The second authorʼs field and herbarium work was supported in part by NSF Doctoral Dissertation Improvement Grant BSR83-14691, an ASPT Herbarium Travel Award, the Missouri Botanical Garden, and the Division of Biology and Medical Sciences of Washington Univer- sity, St. Louis.

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