Monographs Details: Himatanthus attenuata (Benth.) Woods
Authority: Maguire, Bassett & Wurdack, John J. 1958. The botany of the Guayana Highland--Part III. Mem. New York Bot. Gard. 10: 1-156.
Family:Apocynaceae
Description:Distribution and Ecology - VENEZUELA: Amazonas: Maguire, Cowan & Wurdack 30764-A, Cerro Yapacana, Rio Orinoco, eano north of Cerro Yapacana to Rio Orinoco, Jan 6, 1951, tree 10 m tall, flowers white. Maguire, Coivan & Wurdack 30499, Cerro Yapacana. Rio Orinoco, occasional, savanna No. 1, Dec 31, 1950, shrub to 2 m, flowers whitish. Maguire & Wurdack 34495, Alto Rio Orinoco, frequent in scrub near Yapacana cano laguna, northwest base of Cerro Yapacana, elev. 150 m, March 16, 1953, shrub 1.5-4 m, flowers white, fragrant. Maguire, Wurdack & Bunting 36178, Great Rapids of the Orinoco, frequent in open moist area along contact between crystalline laja and Orinoco gallery forest 1 km east of Hotel Amazonas, Pto. Ayacucho, 100-120 m elev., Nov 12, 1953, shrubby tree 3-6 m, flowers white, fragrant. COLOMBIA: Maguire, Wurdack & Bunting 36281, Rio Atabapo, occasional in savanna 1 km west of Cacagual, 130 m elev., Nov 19, 1953, shrub 1-2 m, flowers white, "Platanote."

Discussion:

The first collection cited, 30764A, is strikingly different from the typical plant. The bracts of the inflorescence are very large, about 3.6 cm long and 2.3 cm broad. The corollas are large, about 6.5 cm long (boiled) ; corolla-tube 2.5 cm long, the lobes 4 cm long, 1.5 cm wide, the anthers about 1.8 mm long. The leaves are atypically rounded at the apex and they have strong marginal nerves; petioles 2—4 cm long; blades shining, oblanceolate, gradually and greatly narrowed at the base, 12-17 cm long, 5-7 cm wide, the secondary nerves close and rectlinear, netted venation prominent on both sides. The large bracts and the strong marginal nerves of the leaves are like those of H. bracteat a (A. DC.) Woods., the prominent venation, texture, and luster of the leaves are of good H. attenuata.

The Colombian collection, 36281, is not only very different from the typical plant but also provides a striking contrast with 30764-A. The leaves are sessile or subsessile, very rigid, short (3-9.5 em long), rounded at the apex; inflorescence crowded, small, the bracts oblong, 1-1.5 em long, mostly rounded at the apex; flowers moderate in size (the buds up to 4.5 cm long). The netted venation of the leaves is gross and not sharply raised, the marginal nerve is prominent, and the gloss of the leaf surface is not so strong as usual.

The leaves of the three remaining collections cited above are rounded at the apex, otherwise they are typical. Hybridization has been suggested for the genus, but at present one can only speculate on the reason for the great divergence shown in 30764-A and 36281.

Distribution:Venezuela South America| Colombia South America|