233 



along a creeping rhizome forming a thick, dense turf, erect, i8 to 

 25 cm. high; nodes silky villous with erect hairs; sheaths very 

 slightly inflated, sparsely pilose and hairy at the throat; ligule a 

 rin'g of short hairs; leaves about i mm. wide, pilose, especially 

 the longer ones from the base, upper leaves i 5^ to 3 cm. long, 

 all very acute ; spikes three to six, secund-racemose along the 

 somewhat compressed rhachis. Spikelets two in each cluster 

 with a single, simple or bifid, awn-like rudiment of a third, ses- 

 sile. Empty glumes pilose with rather long, stiff hairs, hirsute 

 at the base, much shorter than the spikelets ; flowering glumes 

 densely hairy at the base and more or less pilose along their 



margins. — Mexico, (Pringle, No. 2,559, 1889; Palmer, 200, 

 1886), 



Pe7itarrJiaphis scahra^ IIBK., has taller, and branched flowering 

 culms, longer and broader leaves, one spikclet only at each node 

 of the main rhachis, and the lower empty glume and the bristle- 

 like rudiments (according to the illustration in Nov. Gen. et 

 Spec.) are simply scabrous (see fig. w, plate CVIII). 



In Pentarrhaphis pauperciila^ {PolyscJiistis paitpcrciila^ Presl), 

 the lower leaves are short, like the upper ones, spikelets single at 

 the nodes of main rhachis, and short pedicel of the second floret 

 (joint of the rhachilla) i^ilose. (See figs, x and x', plate CVIII). 

 According to Presl this species is annual. The descriptions and 

 illustrations of these species given by Kunth and Presl permit of 

 the followHig brief synopsis of them. 



Spikelets two in each cluster, rudiment a single simple or bifid, pilose 



bristle * I. P. Fouknierana. 



Spikelets one in each cluster, rndimentary bristles lliree or four. 



Bristles and pedicel of the second floret scabrous. ..2. P. scahra. 



Bristles and pedicel of the second floret pilose 3, P. I'AUI'ERCula. 



EXPLANATION OF PLATES. 



Plate CV. 

 Male and female plants of Jouvea straniinca^ Fourn.? reduced in size. 



Plate CVL 



iU — A portion of the $ inllorescence. 



b, — A onc-llowered $ spike, enclosed at the base by a leaf. 



