HOW TO KNOW THE GRASSES 



20b. Grain not bottle-shaped nor forcing the floret open; not over 2 mm. 

 long; lemmas not thick and stiff 21 



21a. Spikelets with three or more florets; lemmas pointed, the veins 

 converging; plants of wet or dry ground (NOTE: the Genus Era- 

 grostis, which follows, is a difficult one. No entirely satisfactory 

 key has ever been made for the species found in the U. S. The 

 following keys are compiled from the best available) 22 



21b. Spikelets with two florets; lemmas with wide blunt tips and paral- 

 lel veins; plants aquatic. Fig. 59. 



BROOKGRASS 



Catabrosa aquatica (L.) Beauv. 



Perennial. The culms may lie on the 

 ground and root at the nodes for half 

 or more of their length of 10 — 50 cm. 

 Panicles yellowish, 10 — 20 cm. long, open, 

 pyramidal. Brookgrass is a soft, succu- 

 lent grass of wet ground, found in the 

 sub-arctic and at higher elevations in the 

 western moimtains of the United States. 

 The plants make excellent summer feed 

 for livestock. Found also in northern 

 Europe and Asia. Jiine — August. 



Figure 59 



22a. Plants forming flat mats, the trailing culms rooting at the nodes . . 23 



22b. Plants erect or with somewhat decumbent culms, but never root- 

 ing at the nodes 24 



32 



