Psychotria capitata was described by Ruiz & Pavon from material collected at Chinchao, in the headwaters of the Río Huallaga of the Dept. Huánuco, Peru, apparently from the higher elevations. Peruvian material from the higher elevations, such as at La Merced, above San Ramon, on the Schunke Hacienda, in the Dept. Junin at 1200-1400 meters, shows the stipules less lobed, i e about 1/4-1/3 cut, with the teeth or lobes only 2.5-7 mm long, whereas specimens obtained at the lower altitudes of the Dept Loreto (Alto Río Itaya, La Victoria on Amazon River, Mishuyacu near Iquitos, and Maynas, at 100-145 meters elevation) and from Dept San Martin (Alto Río Huallaga, Lamas, and Tarapoto at 360-900 meters) have stipules more deeply cut (split from 1/3-3/4 distance nearly to the base) with teeth varying from 6-15 mm long. Most of the Peruvian material has inflorescences of an hemispheric type as broad as or broader than high (2-4.5 cm long by 2.5-6 cm broad). The involucral bracts are oblanceolate to lanceolate or oblong-lanceolate. In the specimens from the lower altitudes the lateral nerves of the leaf blades vary in number mainly from 8-16 on each side, whereas those from the higher altitudes have 17-20 lateral nerves on each side.
Psychotria chlorotica M.-Arg. cannot be separated from P. capitata. Standley was indecisive about P. chlorotica and changed his concept throughout his various treatments of South American Rubiaceae. In the Rubiaceae of Bolivia (Field Mus. Publ. Bot. 7: 304. 1931) he maintained P. chlorotica as a distinct taxon, adding in his geographical notes “Also in Peru and Brazil,” but in his treatment of the Rubiaceae for the Flora of Peru he considered P. chlorotica as synonymous with P. capitata, stating (Fl. Peru, Field Mus. Publ. Bot. 13: 187. 1936), “It appears likewise that P. chlorotica Muell.-Arg., a name under which some of the Peruvian material has been distributed, should be reduced to synonymy under P. capitata. The characters used by Mueller in separating P. chlorotica and P. inundata are certainly of little or no importance.”
In some specimens of P. capitata subsp capitata var capitata no bracts are present at the base of the inflorescence (Irwin, Maxwell & Wasshausen 20401; Glaziou 12762; Williams 3304, 3429) or may be present on one inflorescence and absent on another of the same collection (Williams 2960).