Malesian Euphorbiaceae Descriptions
Esser, H.-J. 1999. A partial revision of the Hippomaneae (Euphorbiaceae) in Malesia. Blumea 44: 149215.
Phylogeny of the Hippomaneae
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Sapium Jacq., Enum. Syst. Pl. (1760) 9; nom. cons. [Taxon 43 (1994) 114], non Sapium P.Browne [Civ. Nat. Hist. Jamaica 2 (1756) 338]; A.Juss., Euphorb. Gen. (1824) 49; G.L.Webster, J. Arnold Arbor. 48 (1967) 391; Kruijt, Biblioth. Bot. 146 (1996) 27; G.L.Webster, Ann. Missouri Bot. Gard. 81 (1994) 123; Esser, Blumea 44 (1999) 180; in Radcl.-Sm., Gen. Euphorbiacearum (2001) 373; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11 (2014) 203. Stillingia subg. Sapium (Jacq.) Klotzsch, Arch. Naturgesch. 7 (1841) 187. Stillingia sect. Sapium (Jacq.) Baill., Ιtude Euphorb. (1858) 513; Adansonia 1 (1861) 351. Sapium sect. Eusapium Mόll.Arg., Linnaea 32 (1863) 115, nom. inval.; Pax in Engl. & Prantl, Nat. Pflanzenfam. 3, 5 (1890) 98; T.Post & Kuntze, Lex. Gen. Phan. (1903) 498. Excoecaria sect. Sapium (Jacq.) Mόll.Arg. in DC., Prodr. 15, 2 (1866) 1202. Sapium subg. Eusapium Pax & K.Hoffm. sect. Americana Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.v (1912) 200, nom. inval.; in Engl. & Harms, Nat. Pflanzenfam. ed. 2, 19c (1931) 198. Type: Sapium aucuparium Jacq., nom. illeg. [= Sapium glandulosum (L.) Morong]; compare Kruijt & Zijlstra (1989).
Trees. Monoecious. Leaves present on flowering and fruiting twigs. Indumentum absent. Stipules broadly ovate to triangular, 1.52.5 mm long, undivided, glandless. Leaves regularly spaced; petiole distinct, always less than half as long as the blade, usually apically glandular; blade quite variable, 2.59 cm wide, margin entire or indistinctly serrate with teeth 35 mm apart, glandless above, below usually neither papillate nor whitish-farinose and with marginal glands that often are found in small cilia-like marginal lobes, basal glands hardly different, secondary veins distinct, basal ones not different, intersecondary veins present, tertiary veins usually distinct, indistinctly percurrent to reticulate, smaller veins reticulate. Inflorescences terminal and axillary, yellowish, not compound, pistillate and staminate flowers in same inflorescence. Bracts of staminate cymules with a pair of disc-shaped glands touching the axis of the thyrse. Staminate cymules (3)718-flowered; bracteoles present, mostly small. Staminate flowers with a pedicel c. 0.5 mm long only present when flowering; calyx with 2 largely fused sepals; stamens 2, filaments longer than anthers. Pollen with equatorial ring (fide Kruijt, 1996). Pistillate flowers up to 10 at base of staminate thyrse; pedicel absent to short; ovary 3-locular (1- or 2-locular in some species not in Malesia), smooth; style short, stigmata undivided, glandless. Fruits sessile to shortly pedicellate; 3-seeded (1- or 2-seeded in some species not in Malesia), smooth, dry, opening regularly along the septa, pericarp thin (fruit length/pericarp thickness > 10/1), septa with one vascular strand, remaining columella slightly alate. Seeds completely covered by a red aril.
Distribution 21 species, indigenous and restricted to the Neotropics from Mexico and the Antilles to Argentina and Bolivia. Introduced into the USA, sometimes cultivated in other tropical regions.
Sapium glandulosum (L.) Morong, Ann. New York Acad. Sci. 7 (1893) 227; Kruijt, Biblioth. Bot. 146 (1996) 44 ; Esser, Blumea 44 (1999) 181. Hippomane glandulosa L., Sp. Pl. (1753) 1191. Sapium aucuparium Jacq., Enum. Syst. Pl. (1760) 31, nom. superfl.; Hassk., Retzia 1 (1855) 162. Sapium biglandulosum (L.) Mόll.Arg. var. aubletianum Mόll. Arg., Linnaea 32 (1863) 117, nom. superfl. Sapium aubletianum (Mόll.Arg.) Huber, Bull. Herb. Boiss. 2, VI (1906) 362, nom. superfl.; Burkill, Dict. Econ. Prod. Malay Pen. 2 (1935) 1960. Lectotype (designated by Croizat, J. Arnold Arbor. 24, 1943:, 176): Plukenet, Phytographia Almagestum (1694) t. 229 fig. 8.
Tree, measurements not known in Malesia but up to 20 m tall and d.b.h. up to 40 cm in the Neotropics, slightly buttressed. Bark grey, smooth with irregular longitudinal fissures. Stipules 1.52.2 by 1.22 mm, often persistent. Leaves: petiole 0.82.4 cm long, apically with a pair of distinctly stipitate glands 0.51 mm in diam. usually separate from the blade; blade elliptic to obovate, (5)1017 by 2.56.5 cm, base acute to obtuse, margin serrate when young, later nearly entire, apex acuminate, below with 03 glands per side strictly marginal and in small lateral auricles of the blade 0.41 by 0.51 mm, secondary veins (12)1423 pairs, angle with midrib 6570°, arching but not joined towards the margin, basal ones not differing. Inflorescences: staminate part 60140 by c. 6 mm. Bracts of staminate cymules c. 0.6 mm long, their glands 22.25 mm long and completely on the axis below the bract. Staminate cymules c. 78-flowered. Staminate flowers: pedicel up to 0.5 mm long; calyx 1.25 mm long; stamens with filaments 1.25 mm long when flowering, anthers 0.50.75 mm long. Pistillate flowers c. 510 per thyrse; sessile; calyx 1 mm long, with 3 glandless sepals; ovary 3-locular; style c. 0.5 mm long, stigmata c. 1.5 mm long. Fruits sessile; 3-seeded, nearly circular, 9 mm long, green-brownish; pericarp c. 0.25 mm thick. Seeds c. 5 by 4.5 mm.
Distribution Indigenous to the Neotropics from the Carribean Islands and Mexico to the Guianas and Argentina. In the first half of this century planted in Malesia, e.g. in the Botanical Gardens of Singapore and Buitenzorg.
Habitat & Ecology In the Neotropics found especially in secondary forests and in coastal regions, in the lowland up to 400 m altitude. It is the most common species of the genus.
Uses Planted as a source of rubber. The rubber is of high quality, comparable and in some properties even superior to Hevea rubber, but is difficult to harvest; therefore it never became commercially important. Burkill (1935) mentions use of the poisonous latex against warts. It is also used by Indians to catch birds.
Notes 1. This species is the most variable and taxonomically most problematical one of this difficult genus. Kruijt (1996) suggests to unite 57 names (!) in this species.
2. Burkill (1935) cites two other American species whose cultivation had been tried in Singapore at the beginning of this century, namely S. jenmanii Hemsl. and S. jamaicense Sw. [an illegitimate name for S. laurifolium (A. Rich.) Griseb.: Kruijt (1996) 59]. Both are distinct from S. glandulosum; they may be distinguished, e.g., by their elliptic, hardly obovate leaves with indistinct petiolar glands, S. jenmanii also by its 1-seeded fruits. Because no Malesian specimens of these species were seen, the names cannot be confirmed.