Monographs Details: Rhynchanthera grandiflora (Aubl.) DC.
Authority: Maguire, Bassett & Wurdack, John J. 1958. The botany of the Guayana Highland--Part III. Mem. New York Bot. Gard. 10: 1-156.

Ehyncanthera intermedia Ule, Notizbl. Bot. Gart. Berlin 6: 348. 1915.

Bhyncanthera orinocensis Sprague, Trans. Proc. Bot. Soc. Edinb. 22: 431. 1904.

Gleason (Brittonia 1: 134. 1932.) pointed out the variability in cauline pubescence to be found in the British Guiana specimens of R. grandiflora. Collections since 1932 have obscured the lines between the "well-marked" forms noted by Gleason. Both Ule's and Sprague's collections (as represented at Kew) are so similar as to appear parts of the same collection number; both have longpilose stems. As suggested by Gleason, R. acuminata Benth. and R. betulifolia Cogn., upon comparison with presently available collections, will probably follow R. intermedia and R. orinocensis into synonymy.

R. grandiflora is perhaps the commonest shrub in the Venezuelan morichales and is also frequent in moist areas along roadsides in the llanos. Plants may be found in flower at any time of the year, depending on the seasonal wetness of the habitat. Successive rings of plants flower around a morichal as the water level lowers during the dry season; each plant, as the water level drops, gradually defoliates and ceases flowering. Robust colonies grow in almost soilless but seasonally moist depressions on the crystalline lajas at Puerto Ayaeucho.

As delimited in the past, the genus Potcranthera has been composed of three discordant elements; the species of sect. Onoctonia are congruous with Acisanthera. the generotype seems to belong in the TiboucJiineac as a monotypic genus related to Acisanthera, and the remaining species are well placed in the genus Siphanthera. These adjustments will be treated in detail in a future paper, only one transfer being made at present to accommodate the discussion of a new Venezuelan species of Siphanthera.