Monographs Details: Paralyxia macrophylla (Müll.Arg.) Markgr.
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 - Forest Department of British Guiana Field No. Gappy 479, Record No. 7494, headwaters of Rio Trombetas, Brazil, at the British Guiana frontier, Uranwau, riverside, alt. 1000 ft, Oct 22, 1952, semi-prostrate tree with three stems, 8" X -40', pale yellowish bark, pale yellow slash and wood, white milk, leaves light green, arranged in a spiral near twig ends, flowers white, in subterminal axillary cymes, fruit flat, ear shaped, 2" long.

Discussion:

Figure 15.

The monotypic genus Paralyxia has until now been represented in herbaria only by the Schomburgk type collection made over a hundred years ago on the Tenette hills by the river Takutu in British Guiana. The affinity of this genus has been under discussion (Markgraf, Notizbl. 13: 456-59. 1937). Fortunately, the fruit has now for the first time become available; it suggests a strong link with Aspidosperma, the genus under which the species was originally described. The single meriearp I have before me is a dry dehiscent compressed follicle, almost circular in shape, broadly reniform or ear-shaped, 4.7 cm long, 4 cm wide, 3-6 mm thick, smooth and glabrous; its shallow sinus is about 12 mm across; the curved ridge, which arches over the sinus forming a crescent area on each valve, is 5 mm from the margin at its widest point. The seeds are 4 in number, orbicular, 3.5 cm in diameter, very thin but not papery-winged; the embryo is centrally located, the funiculus is 1.7 long; the cotyledons are coated by a membranous- thin endosperm, orbicular, about 15 mm in diameter, cordate with an open sinus at their base; the radicle is oblong-ellipsoid, about 3 mm long, 1.3 mm thick, slightly surpassing the lobes of the cotyledons. The fruit and seeds are not essentially different from those of Aspidosperma. The flowers also are similar to those of that genus. They do not have, however, the clefts behind the anthers described for Aspidosperma by Woodson (Ann. Missouri Bot. Gar. 38: 124-125. 1951) and suggested as "a rather precise morphological criterion to separate" it from other closely related genera. G. Erdtman examined the pollen grains of 479 and reported that they seem to be very similar to those of Aspidosperma cylindrocarpon, the only species of Aftpidospcrma in his collection.

Distribution:Guyana South America|