Monographs Details: Psychotria caerulea Ruiz & Pav.
Authority: Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.
Family:Rubiaceae
Discussion:

Palicourea caerulea (R. & P.) Roem. & Schult., Syst. Veg. 5: 194. 1819.

Cephaelis polycephala Schlecht., Linnaea 28: 532. 1856, not Psychotria polycephala Benth. in Hook., Jour. Bot. 3: 231. 1841.

"Psychotria brachiata” of many auth., not Sw.

The inflorescence varies in length from 11.5 to 20 cm and in width from 6-9 cm, in general form elongate oblong-pyramical. Usually 12-16 (rarely 10) lateral axes are present in the inflorescence. The hemispherical heads of flowers contain 12 flowers, more or less, and each flower is surrounded by two cucullate bracteoles. The heads of flowers themselves are surrounded by bracts. With this combination of characters, Psychotria caerulea fits into the concept of Cephaelis, and serves as an example of a type intermediate between the generic limits of Cephaelis and Psychotria, i e the bracteoles surrounding each flower in an involucrate head are characters pertaining to Cephaelis, but the well-branched inflorescence is similar to most species of Psychotria.

Psychotria caerulea is closely related to P. brachiata Sw., described from Jamaica, and ranging from the West Indies (Porto Rico, Hayti, Santo Domingo, Cuba, and Trinidad) to Central America. Study of abundant material leads to the conclusion that the two taxa deserve to be treated as distinct species, the largely South American P. caerulea differing in its much larger corollas (11.5-12 mm contrasted with 6-7 mm), exterior surface of corolla densely pilosulous throughout (as contrasted with that of P. brachiata in which the outer surface of the corolla tube is chiefly glabrous, at least below the middle), pubescent interior of the corolla in the lower third, more strongly ciliate calyx margin with the lobes more prominent, larger heads of flowers (7-11 mm in diameter as contrasted with mainly 4-6 mm), more elongated inflorescences (11.5-20 × 6-9 cm as contrasted with 2.5-6 × 3-4.5 cm) with a greater number of lateral axes (usually 12-16 as contrasted with 8-12) which are more elongated and more remote from one another, and larger and longer outer bracts forming an involucre (4.5-7 × 3-6 mm as contrasted with 2.5-3 × 3-3.5 mm). In the Flora of Jamaica by Fawcett & Rendle (7: 99. 1936) the corolla tube is stated to be “glabrous within or nearly so” for P. brachiata. However, there is some variation in this character, ranging from specimens with a short zone of pubescence within, as in Alexander s n to those nearly glabrous within, as in Philipson 1256.