Monographs Details: Psychotria bostrychothyrsus Sandwith
Authority: Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.
Family:Rubiaceae
Description:Distribution and Ecology - Distribution. French Guiana, British Guiana, southeastern Venezuelan Guayana, and northeastern Brazil. FRENCH GUIANA. 1838, Le Prieur 138. BRITISH GUIANA. Mt. Ayanganna below talus along base, NE side, upper Mazaruni River basin, alt 800-900 m, 1 Aug 1960, S. S. & C. L. Tillett & Boyan 44970; gorge below Kaieteur Falls, 10 Sep 1937, Sandwith 1460; Imbaimadai, Mazaruni River, 21 Oct 1951, Fanshawe 3091 (Forest Dept no. 6481); Potaro River gorge, trail from Tukeit to Kaiatuk, 28 Apr 1944, Maguire & Fanshawe 23073; Membaru-Kurupung trail, Cunuria forest, alt 1000 m, 29 Oct-24 Nov 1951, Maguire & Fanshawe 32383; southern Pakaraima Mountains, escarpment to foot of falls, Kopinang Falls, alt 833 m, 2 Sep 1961, B. & C. K. Maguire & Wilson-Browne 46060-A; upper Mazaruni River, woodland near mile 116, Bartica-Potaro Road, alt 600 m, 14 Oct 1951, Maguire & Fanshawe 32111; upper Mazaruni River basin, along Pat Bailey’s line to E end of Karowtipu, Kako River, alt 490 m, 17 Sep 1960, 5. S. & C. L. Tillett 45438. VENEZUELA. Bolívar: Chimanta Massif, trail between Camp 2 and 3, northwestern part of Abácapa-tepui, alt 750-1100 m, 5 Apr 1953, Steyermark 74806; carretera El Dorado-La Gran Sabana, alrededores de km 124, alt 1200 m, 18 Feb 1968, Bunting 2910; Fila de La Danta, between Campamento 125 and Km 127, between Luepa and Cerro Venamo, alt 1200 m, 15-17 Apr 1960, Steyermark & Nilsson 190; woods near campamento 125 at Km 125 between Luepa and El Dorado, alt 1100 m, 14 Apr 1960, Steyermark & Nilsson 87; carretera El Dorado-La Gran Sabana, alrededores de Km 134, alt 1200 m, 19 Feb 1968, Bunting 3002; Serrania del Paujil, 120 km sur de El Dorado, alt 1000 m, 26 Apr 1957, Bernardi 6792; Cerro Venamo (parte suroeste) cerca de los limites con la Guayana Inglesa., entre la base de la ladera principal escarpada de arenisca y el salto en el Río Venamo, alt 1220-1275 m, 6-7 Jan 1964, Steyermark, G. C. K. & E. Dunsterville 92814; Sierra de Lema, summit of low pass, cabeceras de Río Chicanán, 80 km al suroeste de El Dorado, 6° 5' N lat, 62° W long, alt 700 m, 22 Aug 1961, Steyermark 89425; Alto Río Cuyuni, escarpment of La Escalera, Río Uiri-yuk, 20-21 Aug 1962, alt 850 m, B. Maguire, Steyermark & C. K. Maguire 46923; carretera El Dorado-Sta. Elena de Uairen, Km 107, alt 560 m, 13 Aug 1957, Trujillo 3512; del campo km 109 bajando rumbo oeste, alt 450 m, 27 Feb 1959, Bernardi 7310. BRAZIL. Terr. Amapá: Rio Oiapoque, 5 km SE of Clevelandia, 3° 48' N, 51° 53' W, 5 Aug 1960, Irwin, Egler & Westra 47350; Rio Araguari, Serra do Navio, 4 km N of dining and recreation area of ICOML, 20 Jul 1961, Pires, Rodrigues & Irvine 50251.

Discussion:

Type. Anandabaru, Kopinang River, British Guiana, alt 545 m, Apr 1926, Altson 470.

As originally described, this species is most distinct with an elongated, much branched inflorescence. An examination of a suite of material, however, leads to the conclusion that a great range of variation exists within this taxon with respect to the length, width, and ramification of the inflorescence, especially as to number of lateral axes and their length and degree of branching. Most of the material from British Guiana has the inflorescence 22-27 × 16-23 cm with about 20-24 lateral axes, the lowest ones 8-13 cm long and consisting of 4-5 branches on each of the lower axes. However, in specimens from southeastern Venezuela, French Guiana, and Brazil, the inflorescence and lateral axes often become greatly reduced in size and manner of branching, as to resemble such other taxa as P. paniculata (Aubl.) Raeusch., P. deflexa DC. (P. patens), and P. argoviensis Steyerm. As examples of such variations and reductions, it may be pointed out that Steyermark 89425 from southeastern Venezuelan Guayana shows variability even in the same collection from a narrow inflorescence at anthesis to a broader type at fructification, in the flowering state being 8 × 4 cm with only eight well-developed lateral axes but eight others in the upper half not yet developed, whereas in the fruiting stage the infructescence is 12 cm long by 13 cm broad in the lowest part, with a total of approximately 16 lateral axes. The glabrous inflorescences with the axes 4-5-branched and subtended by bracts serve to distinguish this species in bud stage from the closely related P. paniculata, while the sessile flowers in the forks of the axes distinguish it furthermore from P. argoviensis. In the collection of Maguire, Steyermark & C. K. Maguire 46923 a similar situation exists, the young inflorescence 9 × 5 cm with 20 lateral axes (the uppermost crowded and very short), but the infructescence 22-28 × 9-12 cm with up to 44 lateral axes. The specimen of Le Prieur 138 from French Guiana has the same reduced type of inflorescence as that of Trujillo 3512 from the Venezuelan Guayana and those from Territorio Amapá, Brazil. However, none of the above-mentioned collections show the irregular type of branching of the lower axes of the inflorescence nor with all the flowers supported by pedicellate-like stalks, as are present in P. argoviensis, nor do such collections have the narrow stipular teeth of P. argoviensis. The stipular teeth in P. bostrychothyrsus are triangular-ovate or triangular and obtuse to acute, varying from a stipular sheath 2-5 mm long and teeth from only 1 mm long up to 2.5 mm. The pyrenes on their concave ventral face have a shallow and broad longitudinal depression, rather than a narrow deep groove.

Although closely related and often confused with P. paniculata, the present taxon differs from P. paniculata in having a glabrous instead of minutely and sparsely puberulent hypanthium, completely glabrous rachis and inflorescence branches, 20-44 instead of 7-9 lateral axes of the inflorescence, usually conspicuous bracts subtending the flowers and branches of the inflorescence, these lacking or greatly reduced in P. paniculata to low rounded or suborbicular sheaths shorter than half the length of the hypanthium, more conspicuous, ovate-suborbicular, usually glabrous calyx lobes, the lower lateral axes with usually 4-5 branches producing a subracemose-sub-pyramidal shaped inflorescence as contrasted with P. paniculata, in which only 3 short branches are developed at the ends of the lateral axes with one of them much shortened, and with a more conspicuous, thicker marginal nerve developed in P. bostrychothyrsus.

Distribution:French Guiana South America| Guyana South America| Venezuela South America| Brazil South America|