Cephaelis dichotoma Rudge, Pl. Guian. 1: 29. pl. 44. 1805, not Cephaelis dichotoma Willd. ex Roem. & Schult. Syst. 5: 214. 1819.
Psychotria dichotoma (Rudge) Brem., Rec. Trav. Bot. Neerl. 31: 301. 1934, not Psychotria dichotoma H. & B. ex R. & S., Syst. Veg. 5: 190. 1819.
Psychotria martiana M.-Arg., Mart. Fl. Bras. 6(5): 339. pl. 51. 1881.
According to Schott’s itinerary, the Serrada Macacú should be in southern Brazil in Espiritu Santo, Rio province, or Estado Goias. However, Müller-Argoviensis cites the Schott specimen along with those of Blanchet, Prince Neuwied, and Riedel from the state of Bahia.
Psychotria platypoda DC. is characterized by having a glabrous hypanthium and calyx, minute stipular teeth, involucral bracts of the inflorescence arising at the base of the axes of the inflorescence, and glabrous peduncle and axes of the inflorescence. The complete glabrity of the plant distinguishes it from P. barbiflora A.DC. and P. hoffmannseggiana (Willd. ex R. & S.) M.-Arg., in addition to the suborbicular or broadly obovate-suborbicular, rounded, glabrous involucral bracts.
In the fruiting state the axes of the infructescence become lengthened and enlarged laterally, presenting an entirely different aspect from the previous compact, monocephalous appearance in anthesis. Sometimes only one portion of the axes becomes elongated or the axis is elongated only 2 mm (Guppy 192), but in well-developed fruiting specimens (Cayenne, Martin s n), there may be as many as four axes elongated to 10-12 mm. Intermediate lengths of 2-7 mm may be found among the numerous collections cited from Brazil.
From P. contracta M.-Arg. it differs in having broader, glabrous involucral bracts, while from P. lupulina it is at once differentiated by the fewer bracts which are situated at the base of the axes of the inflorescence and not above the base, as in P. lupulina. In P. platypoda some of the flowers are subtended by bracts, but all of them have 2-3 minute glandular processes at their bases, which may represent rudimentary or aborted bracteoles. In addition to the two pairs of decussate involucral bracts (two outermost ones subtending two inner ones) of P. platypoda, other bracts within these two pairs are present, consisting of one larger and two smaller lateral bracts. These interior bracts separate units or groups of 10 to 12 flowers. The innermost groups of flowers are subtended by one or two oblanceolate bracts up to 4 mm long, but most of the flowers are without their own bracts, and are provided only with the aforementioned glandular processes at the base of the ovary.