Monographs Details: Rhynchospora amazonica subsp. guianensis (Kük.) T.Koyama
Authority: Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.
Family:Cyperaceae
Description:Distribution and Ecology - Distribution. So far known from southern and eastern parts of the Guayana Highland. In forests at low altitude. VENEZUELA. Amazonas: Alto Rio Orinco, along Cano Yapacana from laguna to mouth, 125 m alt, Maguire & C. K. Maguire 34590 (NY). GUYANA. [Without further details], Schomburgk 915 (K; fragment in NY). BRAZIL. Rio Negro: Igarape immediately above Barcellos, Rio Cauaburi, Maguire et al 60043 (NY); Amazonas: Manaus-Itacoatiara Highway, Km 201, banks of Rio Urubu, Prance et al 3686 (NY).

Discussion:

Fig 3G-J.

Calyptrostylis longirostris Nees, Companion to Bot. Mag. 2: 394. 1836. Type. Gujana anglica interior, Schomburgk.

Ephippiorhynchium longirostre (Nees) Nees, Fl. Brasil. 2(1): 136. 1842. Based on Calyptrostylis longirostris Nees.

Rhynchospora longirostris (Nees) Steudel, Syn. Pl. Glumac. 2: 145. 1855. Based on Calyptrostylis longirostris Nees. Not of Elliot, 1921.

Rhynchospora amazonica Poepp. & Kunth var guianensis Kükenthal, Bot. Jahrb. 74: 425. 1949. Type. [British] Guiana, Schomburgk 915, in 1840 (K).

The two subspecies of Rhynchospora amazonica are considerably well demarcated by the characters of inflorescences and achenes, though the geographical separation between them is not great. In subsp guianensis the inflorescence consists of three or four distant corymbs, the lateral ones of which are subtended by a sheathing bract, whereas the inflorescence of subsp amazonica is reduced to a single terminal head or a corymb. The style-base in subsp guianensis is long exserted over the fertile glume and is definitely longer than that of subsp amazonica by 6 to 7.5 vs 4 to 4.5 mm in length. The achene body and glumes in subsp guianensis are longer than those of subsp amazonica by % to 1 mm. The hypogynous bristles in the former always surpass the achene body, while in the latter they only equal the achene body. Subsp amazonica could have evolved from subsp guianensis through the reduction in floral parts and inflorescences.

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