Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.
Rubiaceae
Psychotria guianensis Raeusch., Nomencl. ed. 3. 56. 1797, not Mapouria guianensis Aubl., Pl. Guian. 1: 175. pl. 67. 1775.
Psychotria guianensis (Aubl.) Rusby, Mem. Torrey Club 3: 48. 1893.
This complex involves P. barbinervis DC., described from the West Indies, as well as the broad-ranging South American populations of the Guianas, northern Brazil, Venezuela, Colombia, and Ecuador. The divergence encountered over this large area is considerable, but the species complex can be extracted as a recognizable unit, related on the one hand to P. grandifolia, and on the other hand to the P. condensata group. In general, the pubescence of the corolla resembles the P. grandifolia group, and differs from that of the P. condensata group in being shorter and more slender, while the calyx and hypanthium are much smaller than in the P. condensata group.
The variation within the P. guianensis group with respect to the number of cells of the ovary is marked, and appears to have evolved into a geographical pattern with the more easterly distributed populations (Guianas and northeastern Brazil) having 3-4-celled ovaries, while the more westerly distributed populations (Venezuela, Colombia, northwestern Brazil, Bolivia, and Ecuador) show predominantly or exclusively 2-celled ovaries. Within these geographical categories, variation is encountered in hypanthium pubescence, relative proportions of the inflorescence, and external pubescence of corolla.
Bremekamp (Rec. Trav. Bot. Néerl. 31: 283. 1934) examined the Aublet type from French Guiana and reported the number of cells of the ovary to be two, as described by Aublet. However, my own examination of the British Museum specimen of Aublet’s type collection does not corroborate Bremekamp’s observations. Study of an abundant suite of material from French and British Guiana and Suriname shows that the specimens from French Guiana, Suriname, and northeastern Brazil possess 3-4-celled (mainly 4) ovaries, whereas those from British Guiana and countries to the west (Venezuela, Colombia, northwestern Brazil, Bolivia, and Ecuador) have only 2-celled ovaries. All the material examined from French Guiana by me possesses 3-4-celled ovaries. Bremekamp erected special varietal categories for the populations of Suriname, and French and British Guiana with 3- or 4-celled ovaries, but the 3-4-celled condition is the only type I have found throughout French Guiana, where Aublet’s taxon originated, and Suriname, whereas the 2-celled ovary condition persists only in British Guiana and countries to the west of it.
In P. guianensis and P. grandifolia the hypanthium is usually tomentellose, but both taxa possess glabrous variations. Although the lower leaf surface is usually glabrous in P. guianensis and in P. grandifolia var grandifolia, P. guianensis subsp barbinervia has hirsute spreading pubescence on the lower midrib and lateral nerves, nd P. grandifolia var sprucei possesses a more or less pubescent lower leaf surface, including the midrib and lateral nerves.