Schizolobium Vogel, Linnaea 11: 399. 1837.

Figs 67, 68, 69, 70

Type.

Schizolobium excelsum Vogel [= Schizolobium parahyba (Vell.) S.F. Blake]

Description.

Unarmed trees, 25-40 m, the trunk frequently 50 cm and up to 150 cm diameter, often buttressed, saplings typically unbranched to 2-3 m bearing at the apex a cluster of huge, tree fern-like leaves (Fig. 67C), mature trees with a large spreading somewhat flat-topped crown and angular branching (Fig. 67A); bark on young trees green (Fig. 67C, H), later the outer bark thin, smooth silvery-grey, inner bark green (Fig. 67B). Stipules absent. Leaves bipinnate, petiolar gland absent, on young saplings leaves usually very large, up to 2 m long, on mature trees with 15-20 (25) pairs of pinnae and 10-20 pairs of leaflets per pinna, these narrowly-oblong, firm. Inflorescences massive terminal racemose-panicles, pedicels jointed above the middle ( S. amazonicum Huber ex Ducke) or not jointed ( S. parahyba); bracts caducous. Flowers bisexual with an obliquely turbinate hypanthium; sepals 5, free, only weakly imbricate in bud, subequal, reflexing; petals 5, subequal, spreading, clawed, bright yellow, glabrous, oblong-obovate (Fig. 68A); stamens 10, free, equal, equal to or shorter than petals, anthers dorsifixed, glabrous; pollen in oblate tricolporate monads with moderately reticulate surface ornamentation; ovary sessile, affixed to one side of the hypanthium, many ovulate, style filiform, the stigma minute, terminal. Fruits single-seeded flattened, spathulate, oblanceolate or spoon-shaped, rounded at the apex and narrowed at the base to the short stipe (Fig. 70A, B), dehiscent, the valves firm-coriaceous, coarsely reticulately-veined and rugose, dark blackish-brown when mature, from which the endocarp is released intact as a thin, papery wing-like envelope the same shape as the fruit (Fig. 70B). Seeds large, hard, ca. 20 × 12 mm, oblong-ellipsoid, compressed, pale yellow-brown becoming blackish-brown (Fig. 70A).

Chromosome number.

2 n = 26 (Goldblatt 1981b).

Included species and geographic distribution.

Two species, one widespread across the Neotropics from south-central Mexico, Central America, and Amazonia and the second in coastal Brazil from Santa Catarina north to Bahia (Fig. 69).

Ecology.

Mainly confined to terra firme in tropical moist forest and often common in secondary forest. Deciduous, at least briefly, usually flowering when leafless just before leaf flush. Seeds wind-dispersed.

Etymology.

From Greek, schizo - (= split or divided) and - lobion (= fruit), in reference to the splitting of the exocarp from the endocarp at maturity.

Human uses.

Renowned for its fast growth rate and very light soft wood. Widely cultivated as an ornamental and sometimes as coffee or cacao shade; young saplings, with their up to 2m-long leaves resemble tree ferns (Fig. 67C) and are hence sometimes referred to in English as fern trees.

Notes.

Schizolobium is sister to the clade comprising the rest of the tribe (Fig. 66). The distinctive spathulate, oblanceolate or spoon-shaped fruits are unique among Caesalpinioideae (Fig. 70A, B). Although Barneby (1996) reduced the two long-recognised species to varieties of S. parahyba, this was based on limited material, and it is now clear that these two entities are morphologically distinct and occupy allopatric distributions meriting recognition as separate species.

Taxonomic references.

Barneby (1996); Bentham (1870), illustration; Standley and Steyermark (1946).