Trigonostemon villosus var. cordatus, 2018

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 220

c. var. cordatus R.Y.Yu & Welzen , var. nov. — Fig. 17 ; Map 13

A variety found in Sabah resembling Trigonostemon villosus Hook.f. var. borneensis (Merr.) Airy Shaw but differs from the latter by the leaves often being cordate at base and pubescent on the upper surface. — Type: SAN (R. Y. Yu & Jemson) 158479 (holo L; iso SAN ), Sabah, Sandakan, Kabili-Sepilok Forest Reserve. Paratypes: SAN (R. Y. Yu et al.) 158458 (L, SAN ), Sabah, Tepid, Tawai Forest Reserve; SAN (R. Y. Yu et al.) 158459 (L, SAN ), Sabah, Tepid, Tawai Forest Reserve; SAN (R. Y. Yu et al.) 158460 (L, SAN ), Sabah, Tepid, Tawai Forest Reserve; SAN (R. Y. Yu & Jemson) 158480 (L, SAN ), Sabah, Sandakan, Kabili-Sepilok Forest Reserve; SAN (R. Y. Yu & Jemson) 158481 (L, SAN ), Sabah,Sandakan,Kabili-Sepilok Forest Reserve; Stone 6747 (KLU, L), Sabah,Sandakan,Kabili-Sepilok Forest Reserve; SAN (Asik Mantor) 113362 ( SAN ), Sabah, Ulu Sg. Mantuluk Witti Range area.

Leaves: petiole 0.5–2.5 cm long; blade elliptic, 8.5–22 by 3.5–9.5 cm, often cordate at base, pubescent on both sides. Inflorescences unisexual, racemose or thyrsoid, 6–14 cm long, staminate flowers often cauliflorous, a few flowers per node along the rachis. Staminate flowers: sepals elliptic, white; petals claw-like, with a flame-like honey mark near the base. Pistillate flowers: sepals elliptic, green, apex rounded, margin entire, slightly accrescent in fruit; ovary glabrous to densely villose. Fruits green, pubescent.

Distribution — Borneo (Sabah, endemic).

Habitat & Ecology — Lowland rainforests, often on ultramafic soil. Flowering: December to March; fruiting: December.

Note — This variety is sometimes misidentified as T. merrillii because of the hairy leave surfaces, but from its racemose or thyrsoid inflorescences (very few flowers per node, certainly not short paintbrush-like glomerules as in T. merrillii ) it easily differs from the latter species.

Figures

Fig. 17 Trigonostemon villosus Hook.f. var. cordatus R.Y.Yu & Welzen, from Kabili-Sepilok Forest Reserve (a, e, f) and Tawai Forest Reserve (b–d, g), Sabah, Malaysia. a. Growing habit; b. juvenile tree, showing the leaves; c. bark and wood; d. staminate inflorescence; e. staminate flower; f. pistillate flower; g. fruit. — Photos by Ren-Yong Yu.