68 PANICACE.E. 



fiat, or convolute-terete. Sjjikes solitary, on a terminal pedunele, 

 short or long, the clusters of spikelets on the jointed raciiis often 

 surrounded by a ring of hairs. Spikelets of tlie panicle sessile. 



There are 5 or species dispersed over western and south- 

 western North America. 



The genus is readily recognized by each cluster consisting of 

 three spikelets. the central one containing a single fertile flower, 

 either pistillate or perfect, the two lateral ones staminate. 



A. Covered with short dense wool 1 



B. Not woolly (b) 



b. Stoioniferous 2 



b. Xot stoioniferous o, 4 



1. H. rigida (Thurb.) Scribner, Bull. Torr. Club, : 33 (1884). 

 Pkaraphis rigida Thurb. S. Wats. liot. Calif. 'I : '2\n] (1880). 



Branching., 40-00 cm. high, covered with short, dense, white 

 wool. Lisi'ule very short ; lower blades 10 cm. lout', u!)i)er 3-3 

 cm. long, stiir, involute, bristly-pointed. Spike 7. cm. long, 7- 

 10 mm. wide, glumes and palea of the lateral spikes nearly equal ; 

 glumes of the terminal spikelets bifid. 3-nerved. 5-(] mm. long, 

 central nerve excurrent below the middle, the lateral nerves pro- 

 duced as setie ; floral glume 3-nerved; palea aljout ecpud to tlie 

 glume. 



California, Jones; Arizona, Lemnion for U. S. Dept. Agricul. 

 412. 



3. H. cenchroides II. B. K. Nov. Gen. et Sp. 1117 (1815). 



Culms 10-30 cm. high, stoioniferous, frequently rooting at the 

 ])ubescent nodes. Ligule short, laciniate ; blades flat or invohite, 

 narrow. 1-0 cm. long. Spikes 3-4 cm, long. Spikelets with dark 

 glands on the lower half. Outer empty glumes of the empty 

 si)ikelets about 5 cm. long, elliptical, 4-Jierved, one vein becoming 

 a short awn, one-fourth of the distance from the apex; inner 

 empty glume shorter, with a longer awn ; floral glume and palea 

 nearly equal, hyaline, the former eniarginate, 1 -nerved. Empty 

 glumes of the terminal, florets 5-6-nerved, an awn extending half 

 its length above, near the base of which is a ligulate scale ; the 



