Maguire, Bassett. 1967. The botany of the Guayana Highland--Part VII. Mem. New York Bot. Gard. 17: 1-439.
Rubiaceae
Latin Diagnosis - Frutex vel sufffrutex 1.5-4 m, ramis superne 3-4 mm diam glabris, internodiis saepe brevibus 4-10 mm longis ad stipulas dilatatis; stipulis in vaginam sub-truncatam 2.5-3.5 mm longam 6-6.5 mm latam glabram connatis; foliis petiolatis. petiolis 1.1-2 (-4.5) cm longis; laminis elliptico-oblanceolatis apice acutis vel subacuminatis basi cuneatim acuminatis 8-19 cm longis 2.7-4.3 (-6) cm latis utrinque glabris 3 1/2-5-plo longioribus quam latioribus (rariter 2 3/4 -3); inflores-centia convexo-subpyramidali terminali pedunculata in anthesi 2.5-3 cm longi 3.5-4.5 cm lata (pedunculo non incluso) in fructu 3.5-4.5 cm longo 5.5-6 cm lata, rhachidi in anthesi 1-3 cm longa 2-3 mm diam in fructu 3.5 cm longa 3-3.5 mm diam; pedunculo in anthesi 4-7 cm longo 1.7-2 mm lato apicem versus 3-3.5 mm dilatato in fructu ad 8.5 cm longo apicem versus 6 mm lato glabro; infloreseentiae ramis primariis 7-9 subcarnosis albidis in anthesi 7-10 mm longis 1.5-2 mm latis in fructu 10-15 mm longis ubi conjunctis cum rhachidi inaequaliter dilatatis: bracteis infimis sub ramis primariis infloreseentiae ovato-lanceolatis acuminatis 3-4 mm longis glabris; floribus sessilibus plerumque ebraeteatis; bracteis sub nonnullis floribus suborbicularibus obtusis 1 mm longis 1 mm latis glabris; ealyce hypanthioque 1.5-2 mm longo glabro, hypanthio breviter cylindrico 0.7-1.2 mm longo 1 mm lato obtuse angulato; calyce 0.5-1 mm longo 5-lobato, lobis late triangulari-deltoideis obtusis vel subacutis nonnihil inaequalibus 0.3-04 mm longis 0.6-0.8 mm latis glabris; disco depresso 0.2 mm longo tubo calycis breviori; corolla purpurea atque albida hypocrateriformi 10 mm longa, tubo 7 mm longo basi l.8 mm lato fauce 2 mm lato extus glabro intus glabro, lobis quinque ligulato-oblongis apice rotundatis vel obtusis 3 mm longis 1.2 mm latis extus glabris apice appendice incurvata cucullata incrassata 0.5 mm longa munitis: staminibus quinque ad 3/8 longitudinem tubi corollae inclusis. antheris linearibus 2.2-2.5 longis apice minute apiculatis basi angustatis acutiusculis; filamentis 0.5 mm longis glabris supra basim tubi corollae 2 mm insertis.
This species has been confused with Psychotria chlorantha Benth., from which it differs in many respects. The type collection of P chlorantha (K), which I have examined, was based upon Robert Schomburgk 468 from Surrysurrero, British Guiana. An examination of this specimen, together with other collections conspecific with it, show the following differences between P chlorantha and P. amplinoda: (1) In P chlorantha the main branches of the inflorescence are quadrangular, or relatively the same thickness and diameter throughout, and not enlarged at the junction of the main axis of the inflorescence with the lateral axes. In contrast P. amplinoda the main branches of the inflorescence are flattened, not angled, and conspicuously enlarged at the junctions of the main axis with the lateral axes of the inflorescence. (2) The leaf-blades, while of similar shape, have very different nervation. In P chlorantha there are usually about 8 pairs of lateral nerves impressed above and elevated beneath, whereas in P. amplinoda the nerves are much less developed and scarcely evident. (3) In P. amplinoda the internodes of the upper part of the stems are more numerous, 0.5-2 cm apart, whereas in P chlorantha they are fewer. (4) The nodes of the stems in P. amplinoda are conspicuously enlarged to a dilated truncate stipule, whereas in P. chlorantha they are not enlarged. (5) In P chlorantha the throat of the corolla is white-bearded within, whereas in P. amplinoda it is glabrous. (6) In P. chlorantha the corolla is greenish or greenish-white, in P amplinoda it is purple with white or lavender, and longer than in P chlorantha (9-10 mm long in P. amplinoda vs. 2.5-3 mm long in P. chlorantha). (7) In P chlorantha the calyx is minutely ciliate at the truncate or shallowly undulate apex, whereas in P amplinoda it is glabrous and prominently deltoid-lobed. (8) In P chlorantha the cyme is more flat-topped and subcorymbose, and always much broader than high, whereas in P. amplinoda it is convex-subpryramidal and often higher than broad. In P chlorantha the inflorescence is also distinctly trichotomous with the lowest primary branches meeting exactly opposite, whereas in P. amplinoda the lowest branches are enlarged at their place of origin and less obviously meeting exactly opposite. (9) In P chlorantha the angles of the branches of the inflorescence show a line of tomentulose puberulence, whereas in P. amplinoda they are completely glabrous. (10) In P. amplinoda the peduncle much exceeds the petiole, whereas in P chlorantha the peduncle about equals or is only slightly longer than the petiole. (11) Finally, it will be noted that the habitat of P. chlorantha is found in lowland altitudes, whereas that of P. amplinoda is from elevations of sandstone escarpments and summits of table mountains from 625 m at Tafelberg to 2200 m on Ptari-tepui.
In addition to the type specimen of Psychotria chlorantha, the following specimens have been identified as conspecific with P. chlorantha: BRITISH GUIANA. Haieka savanna, east side of Haieka river, Tillett, Tillett A Boyan 45220; Sandwith 324- SURINAME. Tafelberg, Maguire A Stahel 23735, 23729.