Plukenetia, (Hassk.) Mull. Arg.

Cardinal-McTeague, Warren M. & Gillespie, Lynn J., 2020, A Revised Sectional Classification of Plukenetia L. (Euphorbiaceae, Acalyphoideae) with Four New Species from South America, Systematic Botany (Basel, Switzerland) 45 (3), pp. 507-536 : 517

III. PLUKENETIA sect. HEDRAIOSTYLUS (Hassk.) Müll.Arg., D.C. Prod. 15 (2): 772. 1866 .

Hedraiostylus Hassk., Tijdschr. Natuurl. Gesch. Physiol. 10: 141. 1843. Sajorium sect. Hedraiostylus (Hassk.) Baill., Étude Euphorb. 483. 1858.

TYPE: Hedraiostylus glaberrimus Hassk. [= Plukenetia corniculata Sm. ]

Plukenetia sect. Sajor Müll.Arg., Linnaea 34: 159. 1865. TYPE: not designated.

Plukenetia sect. Pterococcus (Hassk.) Benth. & Hook., Gen. Pl. 3, 1: 327. 1880. Pterococcus Hassk. , Flora 25 (2, Bleibl.): 41. 1842, nom. cons., non. Pall. 1773. TYPE: Pterococcus glaberrimus (Hassk.) Hassk. [= Plukenetia corniculata Sm. ]

Vines, lianas, or perennial herbs, stems slender, twining or sometimes procumbent. Leaf venation palmate, primary veins 3(–5). Inflorescences bisexual racemes (rarely racemose thyrses); pistillate flowers solitary (rarely 2) at basal-most node(s); staminate flowers 1/node (sometimes 1–2/node in reduced condensed cymules). Staminate flowers: receptacle convex, subglobose, or globose; nectaries absent; stamens 8–20, densely packed; filaments conical, <0.5 mm long; pollen P = 34–40 m m, E = 40 –50 m m, tectum foveolate. Pistillate flowers: styles entirely connate into a depressed-globose or stout-cylindrical column, 0.5–1.4 mm long, or;70% connate into a stout-cylindrical column with spreading free style arms, 1.3–1.7 mm long. Fruits 4-lobed capsules, dry, dehiscent, 1.1–2 cm in diam. Seeds broadly lenticular, 5.5–10.5 ˟ 5–8 ˟ 2.5–8 mm (“small” or “medium” sensu Cardinal-McTeague et al. 2019a).

The species in this section are distributed in southern Africa and Southeast Asia.

Discussion —Section Hedraiostylus refers to a strongly supported clade within subclade P5 ( Fig. 1 ) and includes three species, P. africana and P. procumbens from southern Africa and P. corniculata from Southeast Asia. This section is weakly defined morphologically but appears to be united by short styles <2 mm long, usually shorter than the length of the ovary (although slightly longer than the ovary in P. procumbens ), staminate flowers with short-conical filaments and lacking nectaries, smaller dry dehiscent fruits, and “small” or “medium” seeds. The southern African species are unique for growing in seasonally dry wooded savannas and have evolved thick rootstocks that facilitate resprouting after fires.

Figures

FIG.1. Summary cladogram of the relationships recovered by Bayesian analysis of combined and partitioned ETS,ITS, KEA1 introns 11 and 17, TEB exon 17, matK, and ndhF DNA sequence data of Plukenetia and Romanoa (modified from Cardinal-McTeague et al. 2019a), highlighting our revised sectional classification of Plukenetia. Maximum parsimony bootstrap percentage (MPBP) and Bayesian posterior probability (BPP) support values> 50% are indicated on each branch. Branches in bold indicate strong support ($ 85 MPBP and $ 0.95 BPP). Subclade numbering system (P1–P5) follows Cardinal-McTeague and Gillespie (2016). Sections in the pinnately veined clade (P1 + P2) are indicated by light grey boxes,sections in the palmately veined clade (P3–P5) by dark grey boxes; new species are indicated in bold. A–B. Leaf clearings demonstrating leaf architecture (images from Gillespie 1993). A. P. stipellata, Gillespie 413 US. B.P. supraglandulosa, Granville 3626 CAY.C–D. Scanning electron micrographs demonstrating pollen tectum morphology (images from Gillespie 1994). C. P. stipellata, Gillespie 418 DAV. D. P. loretensis, Maguire & Politi 27371 US.