1957] 



THE BOTANY OF THE GUAYANA HIGHLAND— PART II 



259 



Annual; culms decumbent spreading, rooting at the nodes, rather freely branch- 

 ing, as much as 50 cm long, the internodes of nearly equal length, glabrous; 

 sheaths about half as long as the internodes, sparsely pilose to glabrous; ligule 

 thin ? 0.5 mm long, high-arcuate; blades ascending or appressed, 2.5-4.5 cm long, 

 5-9 mm wide, acute, narrowed toward the base but rounded and clasping the culm, 

 pilose on the upper surface near the base; panicles as much as 9 cm long, nearly 

 as wide, the solitary branches ascending with filiform divergent branchlets, 

 pilose in the axils; spikelets 1.2 mm long, glabrous, the filiform pedicels much 

 longer than the spikelets; first glume narrow, acute, half as long as the spikelet; 

 second glume obtuse, 2/3-3/4 as long as the fruit; sterile lemma acute, ex- 

 ceeding the fruit, containing a staminate flower; fruit acute, plano-convex, white. 



TYPE: locally abundant around laja at mouth of Cano Arapacua, Rio Paci- 

 moni, alt. 120 m, Amazonas, Venezuela, April 8, 1953, Bassett Maguire & John 

 /. Wurdack 34917; U. S. National Herbarium No. 2,116,125. 



Panicum petrense Swallen, sp. nov. 



Annuum; culmi graciles, caespitosi, erecti, 25-30 cm alti, ramosi, ramis ap- 

 pressis; vaginae internodiis paulum breviores; ligula arcuata, tenuis, 0.3 mm 

 longa; laminae 1.5-3 cm longae, 1.5-3 mm latae, vel superiores breviores, glabrae 

 vel basi sparse pilosae; paniculae 1.5-3 cm longae, ramis gracilibus scaberulis 

 anguste adscendentibus; spiculae 1.2-1.3 mm longae, pilosae; gluma prima acuta 

 vel subobtusa spicula 1/2 brevior; gluma secunda obtusa, fructu 1/4-1/3 brevior; 

 lemma sterile acutum fructu longius; fructus 0.8 mm longus, ovatus, albidus, stria- 

 tus. 



Annual; culms slender, densely tufted, erect, 25-30 cm high, rather freely 

 branching, the branches appressed; sheaths a little shorter than the internodes or 

 overlapping on the branches; ligule arcuate, very thin, about 0.3 mm long; blades 

 1.5-3 cm long, 1.5-3 mm wide, or the uppermost smaller, bluish-green, ascending 

 or appressed, glabrous or with a few scattered long hairs toward the base; pani- 

 cles 1.5-3 cm long, the slender usually solitary branches narrowly ascending, or 

 somewhat spreading at maturity, scaberulous; spikelets 1.2-1.3 mm long, pilose; 

 first glume acute or subobtuse, half as long as the spikelet; second glume 2/3- 

 3/4 as long as the fruit; sterile lemma pointed beyond the fruit, enclosing a 

 palea and staminate flower; fruit 0.8 mm long, ovate, white, striate. 



TYPE: abundant in moist sand on exposed rocks, 15 km above San Fernando 

 de Atabapo, Rio Atabapo, Rio Orinoco, Amazonas, Venezuela, October 17, 1950, 

 Bassett Maguire 29259; U. S. National Herbarium No. 2,040,198. 



Panicum gracilissimum Swallen, sp. nov. 



Annuum; culmi gracilissimi, erecti vel adscendentes, simplices vel ramosi, 

 internodiis superioribus 3.5-5 cm longis; vaginae internodiis multo breviores, 

 glabrae; ligula arcuata, tenuis, 0.5 mm longa; laminae 7-18 mm longae, 0.5- 

 1.3 mm latae, appressae, glabrae vel sparse pilosae; paniculae 3-5 cm longae 

 ramis filiformibus solitariis adscendentibus in axillis pilis longis; spiculae 

 1-1.2 mm longae, pilosae vel papilloso-pilosae, pedicellis filiformibus 3-4 mm 

 longis; gluma prima acuta spicula 1/2 brevior; gluma secunda obtusa fructu 1/4- 

 1/3 brevior; lemma sterile acutum, fructu longius; fructus acutus, lucidus, albus. 



Annual; culms very slender, erect or ascending, 24-28 cm high, simple or 

 branching, the upper internodes mostly 3.5-5 cm long; sheaths much shorter than 

 the internodes, glabrous; ligule arcuate, thin, 0.5 mm long; blades 7-18 mm long, 

 0.5-1.3 mm wide, glabrous or sparsely pilose, usually appressed; panicles 3-5 cm 

 long, or those of the branches smaller, the solitary, filiform branches and branch- 



