Croton simalurensis J.Beyer, 2023

Beyer, J., Esser, H. - J., Eurlings, M. C. M. & Welzen, P. C. van, 2023, A revision of the genus Croton (Euphorbiaceae) in Sumatra (Indonesia), Blumea 68 (1), pp. 1-25 : 19

14. Croton simalurensis J.Beyer , sp. nov. — Fig. 6

Characteristic for C. simalurensis are stalked leaf glands placed abaxially at the very base of the leaf, close to but not on the midrib; scattered but distinct trichomes on abaxial leaf side; large densely pubescent 3-lobed oblate capsules. Croton simalurensis was confused with C. laevifolius but can easily be distinguished by the location of leaf glands, as C. laevifolius has them on the apex of the petiole instead of the leaf blade. — Type: Achmad 298 (holo L [L.2203305]!; iso U [U.1256144]!), Indonesia, Sumatra, Aceh, Simaloer (Simeulue).

Paratypes: Achmad 99 ( U [ U.1256142]!); Achmad 286 ( L [ L.2203303]!, U [ U.1256145]!); Achmad 299 ( L [ L.2203304]!, U [ U.1256143]!); Achmad 482 ( L [ L.2203861]!); Achmad 870 ( L [ L.2203858]!); Achmad 1100 ( U [ U.1256146]!); Achmad 1780 ( L [ L.2203850]!),all Achmad collections from: Indonesia, Sumatra, Simaloer ; Rahmat Si Boeea 9364 ( L [ L.2203848]!), Indonesia, Sumatra East Coast , Asahan , Aek Moente ; Rahmat Si Boeea 9519 ( L [ L.2203849]!), Indonesia, Sumatra East Coast , Asahan , Tor Ma- toetoeng; Rahmat Si Boeea 10029 ( L [ L.2203846]!), Indonesia, Sumatra East Coast , Asahan , Tomoean Dolok .

Woody, probably shrubs or trees; young branchlets densely pubescent, only partially glabrescent. Indumentum consisting of stellate trichomes, yellowish brown in the centre with whitish radii, 0.3–0.6 mm diam (0.1–0.6 mm diam on stems and capsules), flat (sometimes not flat on stems), with a central porrect radius, with (8–)15–25 free (or fused) radii. Stipules ensiform to subulate (occasionally narrowly triangular), 3–7(–9) by (0.4–) 0.8–1.5 mm, densely pubescent on both sides. Leaves alternate; petiole (0.5–) 1–5 cm long, slightly grooved above, with scattered but distinct trichomes to puberulous; glands abaxially at the very base of the leaf, close to but not on the midrib,slightly to distinctly stalked discs, (0.4–) 0.6–1 mm diam, stalk 0.1–0.3 mm long; blade elliptic to obovate, 5.5–18 by 2.7–7.5 cm, 1.7–2.8 times longer than wide, chartaceous, base cuneate to obtuse, sometimes nearly rounded, margin in young leaves subserrate, soon almost entire, never with trichomes or glands at teeth, apex acuminate (rarely obtuse to rounded), adaxial side glabrous, abaxial side lighter than adaxial side when dried, trichomes scattered but distinctly pubescent (with surface always visible), more densely pubescent on the midrib and near the base, hardly glabrescent; venation distinct, sunken above, basally not triplinerved, secondary veins 8 –10 pairs, higher order veins distinct below. Inflorescences 1(–4) per apical node, (7–) 10–20 cm long, erect, basally 3–9 pistillate flowers, often 1 or 2 staminate flowers on same node as a pistillate flower, apically 1–4 staminate flowers per node; bracts triangular-ovate, 1.5–2.5 by 0.8–1.2 mm, subglabrous except for patch of simple trichomes on apex, quite persistent. Staminate flowers 3–4 mm diam; pedicel 1.5–4 mm long, round, with scattered trichomes to glabrous; sepals ovate, c. 2 by 1.5 mm, fused at base, subglabrous outside; petals oblong, c. 2 by 0.5 mm, outside glabrous; stamens 10–12, free, filaments 2.5–3.5 mm long, anthers c. 0.7 by 0.4 mm. Pistillate flowers 5 –6 mm diam; pedicel 3 – 6 mm long with scattered but distinct trichomes to puberulous; sepals ovate to elliptic, c. 3 by 2 mm, fused at very base, apex acute, outside puberulous near base to glabrous near apex, with patch of simple trichomes on apex, inside glabrous, longer than ovary; petals filiform, c. 2 by 0.1 mm, usually absent; ovary globose, c. 2 by 2 mm, very densely yellowish pubescent, style less than 0.1 mm long; stigmas 2.5–4 mm long, thickened at base, once divided to 1.5–3 mm from apex. Capsules distinctly 3-lobed, oblate, 7–9 mm high by 10–12 diam, lobes conchiform, heavily sulcate, surface rough, densely pubescent, apex slightly depressed; pericarp 0.4–0.6 mm thick; columella 6–7 mm long. Seeds ovoid, c. 6 by 5 mm, glabrous, carunculate.

Distribution — Malesia: Endemic to Sumatra (Aceh (Simalur Isl.), Sumatera Utara).

Habitat & Ecology — Altitude: to 1000 m. Flowering: January, March, June–August; fruiting: March, June, November.

Affinities — Riau pocket group ( Van Ee et al. 2015).

Vernacular names — Dulu Dulu, Lasa-Lasa (Simalur); Kajoe depdep batoe (Rahmat Si Boeea 9364); Kayu Polir Aek (Sumatera Utara).

Notes — 1. No ecological information is known from the collections of Sumatra, where it was mainly collected on Simalur island.

2. The capsules can be affected by insects and become galled, being larger and seemingly more than 3-locular.Affected capsules are also less pubescent than regular ones and they are more oblate in shape. Highly affected capsules often have 1 to 3 holes in their pericarp possibly made by the insects.

Figures

Fig. 6 Coton simalurensis J.Beyer. a. Habit; b. basal leaf glands, slightly elevated; c. staminate flower; d. staminate flower with part of sepals and petals removed; e. pistillate flower with part of sepals removed; f. fruit; g. part of fruit wall of septicidally dehisced fruit; h. columella; i. seeds in lateral and front view, with lighter colour (no caruncle) (a–d: Achmad 299; e: Rahmat Si Boeea 9519; f–i: Achmad 298; all L). — Illustration by Esmée Winkel, 2022.