Monographs Details: Panicum fonticolum Swallen
Authority: Maguire, Bassett & Wurdack, John J. 1957. The Botany of the Guiana Highland -- Part II. Mem. New York Bot. Gard. 9 (3): 235-392.
Family:Poaceae
Description:Latin Diagnosis - Annuum? Culmi 20-35 cm longi, adscendentes, parte inferiore decumbentes vel prostrati; vaginae glabrae vel sparse pilosae internodiis multo breviores; ligula 0.4 mm longa, tenuis, truncata; laminae 2-3.5 cm longae, 2-4 mm latae, acuminatae, patentes, glabrae, tenuis; paniculae 2.5-6 cm longae, ramis solitariis adscendentibus ex basi ramosis; spiculae 1.3-1.4 mm longae, ellipticae vel obovatae, acutae, sparse pilosae; gluma prima angusta, acuta, 1-nervis, spicula 1/3-1/2 brevior; gluma secunda et lemma sterile aequalia fructu longiora; fructus 1 mm longus, ellipticus, subobtusus, albus, striatus.

Species Description - Annual? Culms 20-35 cm long, ascending, the lower part decumbent or prostrate with short internodes, leafless or the leaves soon deciduous, the upper internodes gradually longer; sheaths glabrous or very sparsely pilose, much shorter than the internodes; ligule thin, truncate, about 0.4 mm long; blades 2-3.5 cm long, 2-4 mm wide, acuminate, somewhat narrowed toward the base, thin, spreading, glabrous; panicles 2.5-6 cm long, the slender solitary branches stiffly ascending, branching from near the base, the branchlets spreading, few-flowered; spikelets 1.3-1.4 mm long, elliptic or obovate, acute, sparsely pilose; first glume 1/2-2/3 as long as the spikelet, narrow, 1-nerved, acute; second glume and sterile lemma equal, pointed beyond the fruit, the lemma without a palea or staminate flower; fruit 1 mm long, broadly elliptic, subobtuse, white, striate.

Discussion:

TYPE: on waterfall, in spray, Culebra Creek, alt. 1500-1600 m, Cerro Duida, Rio Cunucunuma, Amazonas, Venezuela, November 21, 1950, Bassett Maguire, R. S. Cowan & John J. Wurdack 29636; U. S. National Herbarium No. 2,040,215.

Resembling Panicum rivale Swallen, but differing in having shorter-pediceled, pilose spikelets, truncate rather than arcuate ligule, and acuminate blades.

The following seven species, with P. wurdackii and P. steyermarkii, are related to Panicum loreum Trin. Other species of this group previously described from the Guayana Highland are P. eligulatum N. E. Brown, P. tropidoblephore Tutin, P. curvifolium Swallen, and P. tatei Swallen. All are similar in habit, but differ markedly in specific characters. With the exception of P. sipapoense which has a short ligule, there is no differentiation between sheath and blade.