Monographs Details: Posoqueria latifolia subsp. gracilis (Rudge) Steyerm.
Authority: Maguire, Bassett. 1967. The botany of the Guayana Highland--Part VII. Mem. New York Bot. Gard. 17: 1-439.
Family:Rubiaceae
Description:Distribution and Ecology - The Guianas, southern Venezuela, amazonian Brazil; doubtfully from Colombia. FRENCH GUIANA. Montagne de Kaw, Cowan 38702. SURINAME, near Km 11 in montibus Nassau, Lanjouw & Lindeman 2774; Wilhelmina Gebergte, 3°36'-3041'N, 56°30'-56°34'W, 1 km SE of Juliana Top, headwaters of West Rivier, Irwin, Prance, Soderstrom & Holmgren 55107. VENEZUELA. Amazonas: Alto Rio Orinoco, along Rio Padamo about 15 km above mouth, Maguire & Wurdack 34735; Upper Orinoco, Tamatama, Williams 15259; Cerro Huachamacari, intalus forest near Camp II, alt 1100 m, Maguire, Cowan & Wurdack 29797; Cerro de la Neblina, limite Venezuela-Brazil, alt 1500 m, Ewel 205. BRAZIL. Amazonas: Cucuhy, Rio Negro superior, Ducke 34992 (type of Posoqueria brachyantha).

Discussion:

Solena gracilis Rudge, Pl. Guian. 27, t. 41. 1806.

Posoqueria gracilis (Rudge) R. & S., Syst. Veg. 5: 227. 1819.

Posoqueria brachyantha Standley, Field Mus. Publ. Bot. 22: 120. 1940.

Type. “A fluvio Dorapu ad Kaw,’’ French Guiana.

The Cowan 38702 collection comes from the vicinity of the type locality. The Venezuelan material cited under subsp gracilis differs from the French Guiana and Suriname specimens in having rounded calyx-lobes and more prominently nerved leaves on their lower sides. The type specimen of P brachyantha Standley shows only one flower in early anthesis, the remainder of the flowers being in bud. The longest corolla-tube (that of the flower in early anthesis) is 6 cm long, but more mature corollas probably attain another centimeter in length. In all other respects, Standley’s description and a study of the type specimen matches in all other particulars Rudge’s taxon of French Guiana.

Study of Solena latifolia Rudge, upon which Posoqueria latifolia is based, shows that it is a taxon of more limited geographical distribution than that which has been assigned to it previously. It is chiefly a taxon of the lower elevations, relatively short corolla-tubes glabrous within except for some minute puberulence in the basal part, and coriaceous dark green leaf-blades with inconspicuous and usually immersed lateral nerves of the lower surface. Rudge’s pl. 40 (Pl. Guian.) shows ovate-triangular, acute stipules 10-11 mm long and 6-7 mm broad at the base, and is matched by specimens from the Guianas. Rudge’s plate shows a relatively short corolla-tube (8.5 cm long by 3-3.5 mm broad). True P latifolia has been confused by many authors with the montane plants of the higher elevations of the Coastal Cordillera and Andes of Venezuela and Colombia, referred in the present treatment to P. coriacea subsp formosa (based on Stannia formosa Karst.), in which the interior of the corolla-tube is found to possess characteristic vesicles lining the surface of the tube.

Posoqueria gracilis, based on Solena gracilis Rudge, is described and illustrated by Rudge (Pl. Guian. 27, t. 41 with fewer flowers and smaller leaves with shorter or mainly absent stipules than those encountered in true P latifolia. However, study of the available material indicates that P. gracilis cannot be maintained as a taxon distinct from P. latifolia because of intergradations in leaf-size and shape and in length of corolla-lobes on the same plant. Although P. gracilis may eventually have to be merged with P latifolia, it is retained for the present as a subspecies differing in general from subsp latifolia by the usually smaller leaves, and smaller, generally deciduous, stipules.

The present study indicates that P. latifolia can be separated from P. trinitatis, P panamensis, and P. coriacea by various characters which have been overlooked by previous authors in their treatments of the genus.

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