Croton tiglium

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 : 19-20

15. Croton tiglium L.

Croton tiglium L. (1753) 1004; Müll.Arg. (1866) 600; Hook.f. (1887) 393; Merr. (1921a) 337; (1923) 427; Ridl. (1924) 262; Gagnep. (1925) 285; Merr. (1926) 382; Burkill (1935) 690; Merr. (1935) 236; Backer & Bakh.f. (1963) 477; Airy Shaw (1972a ‘ 1971 ’) 250; Whitmore (1973) 84, in obs.; Airy Shaw (1975) 95; (1981a) 285; (1982a) 15; (1983) 20; Corner (1988) 284; Chakrab. & N.P.Balakr. (1997 ‘1992’) 72, map 3; Philcox (1997) 94; Esser (2005) 222; P.T. Li & Esser (2008) 262; Chakrab. (2019) 3630. — Tiglium officinale Klotzsch (1843b) 418. — Oxydectes tiglium (L.) Kuntze (1891) 614. — Croton officinalis (Klotzsch) Alston (1931) 264, nom. illeg., superfl. — Lectotype (first step designated by Chakrabarty & Balakrishnan 1997;second step by Philcox 1997): Herb.Hermann 2: 6, no. 343 (lecto BM [BM000621766]*), Sri Lanka.Other original material: BM [BM000621766]* (Herb. Hermann 2: 76, no.343), [BM000621811]* (Herb.Hermann 3: 6, no. 343), [BM000628053]* (Herb. Hermann 4: 10 no. 343]), Sri Lanka.

Croton glandulosus Blanco (1837) 754 (‘glandulosum ’), nom.illeg., superfl., non L. (1759). — Croton muricatus Blanco (1845) 518,nom. illeg.,superfl., non Vahl (1807); (1879) 154, t. 383. — Oxydectes blancoana Kuntze (1891) 610. — Neotype (designated here): Merrill Species Blancoanae 308 (neo L [L.2212332]!), Philippines, Luzon, Camarines Prov. See also Merrill (1918: 220).

Croton jatrophifolius Müll.Arg. (1866) 600 (as ‘ jatrophaefolius ’). — Oxydectes jatrophifolia (Müll.Arg.) Kuntze (1891) 612. — Type: Anonymous s.n. (holotype G-DC [G00311911]!), Indonesia, Banda (misformed). Syn. nov.

Croton tiglium L. var. globosus J.J.Sm. (1910) 349. — Lectotype (designated here): Koorders 14426 (lecto L [ L.2212249]!; isolecto L [ L.2212250]!, U [ U.1256074]!), Java, Prov. Besoeki, Pantjoer Idjen , 1000 m. Syn. nov.

For other synonyms see World Flora Online (http://www.plantsoftheworl- donline.org/); more will be incorporated when other regions of Malesia are treated.

Shrubs or trees, to 6 m tall, diam to 15 cm; young branchlets with scattered trichomes, soon glabrescent. Indumentum consisting only of yellowish stellate trichomes, 0.2–0.9 mm diam on leaves, up to 0.5 mm on stems, flat, often with a short central porrect radius, with 9–15 free radii. Stipules filiform to ensiform, (0.5–)1.5–3(–4) mm long, densely pubescent on both sides to subglabrous, caducous. Leaves alternate; petiole 3–8(–10) cm long, hardly to shallowly grooved above, with scattered trichomes to subglabrous; glands always lateral on the basal leaf margin close to but not on the midrib, 0.5–1 mm diam, sessile to slightly stalked (always less than 0.5 mm long), marginal teeth often topped by colleters; blade ovate (to elliptic), 6–18.5 by 4–9 cm, (1.7–)1.9–2.3 times longer than wide, membranous, base obtuse with very base attenuate, margin slightly serrate to subentire, teeth 3– 6 mm apart, without glands, apex mostly acuminate, sometimes acute, abaxial side slightly lighter then adaxial side when dry, with scattered trichomes to subglabrous on both surfaces, sometimes more densely pubescent at the very base of the bigger veins, epidermis visible; venation very distinctly triplinerved, actinodromous, with 3(–5) prominent basal veins, secondary veins 4–6 pairs. Inflorescences thyrsoid, 1–3 per whorl, (4–) 7–13 cm long, erect, basally 4–10 pistillate flowers, sometimes 1 or 2 staminate flowers at the same node as a pistillate flower, apically 1–3 staminate flowers per node; axis with scattered trichomes to subglabrous; bracts triangular-ovate, 2–4 by 0.5–1 mm (staminate ones smaller than pistillate ones), quite glabrous, eglandular, caducous to persistent. Staminate flowers 4–4.5 mm diam; pedicel 3–5 mm long, subglabrous; sepals triangular-ovate, c. 2.5 by (1.5–) 2 mm, subglabrous outside; petals oblong, c. 2 by 1 mm, glabrous outside; stamens 15–20, free, filaments 1–3.5 mm long, anthers c. 0.6 by 0.5 mm. Pistillate flowers 6– 8 mm diam; pedicel 3–5 mm long, densely pubescent; sepals triangular, 2.5–3.5 by 1–2 mm, fused at base, apically spreading, slightly longer than ovary or as high, outside subglabrous, with a patch of simple trichomes on the very apex; petals absent; ovary distinctly 3-locular, globose to slightly ovoid, 3–4 by 2–3 mm, densely pubescent; stigmas 4–6 mm long, once divided to 3–4 mm from apex. Capsules 3-lobed, prolate, 18–25 by c. 15 mm, sulcate, surface with scattered trichomes to subglabrous; pericarp fragile and thin (less than 1 mm thick); columella c. 17 mm long. Seeds prolate, one side slightly flattened, c. 13 by 8 mm, glabrous, with small caruncle.

Distribution — Naturally occurring in Sri Lanka, India, through SE Asia to China, and in Malesia from the Malay Peninsula to the Philippines and the Moluccas, though it is often not possible to ascertain if a specimen was collected in the wild (check https://powo.science.kew.org/taxon/urn:lsid:ipni.org: names:343631-1; last visited on 5 August 2022). Cultivated and introduced in North America and Africa. On Sumatra in Sumatera Utara, Sumatera Barat, Jambi.

Habitat & Ecology — Mostly in evergreen secondary forest. Altitude: sea level to 1100 m. Flowering: May–October; fruiting: May–August.

Affinities — Croton section Croton ( Van Ee & Berry 2010b) .

Vernacular names — Simalakian ( Burkill 1935); Croton oil plant (English).

Uses — Burkill (1935): Seeds or oil of seeds is used in very low doses (at most 1 seed or 1 drop) as purgatives, but very poisonous (blistering mouth and intestines if too much, blistering and inflamating skin); therefore also used for poisoning humans, and in hunting to stupefy fish or to make poison arrows (bark and leaves also suitable for that purpose). The seed oil can also be used for illumination, but only outdoors as the fumes are poisonous, same if the wood is used as firewood. Still, in former times planted for the seed oil, which was exported to Europe; today the market is limited to some medical treatments, especially for skin peeling.