HOW TO KNOW THE GRASSES 



7b. Rachilla not prolonged beyond the base of the upper floret. Fig. 



181. 



SILVER HAIRGRASS Aira caryophyllea L. 



Annual; tufted; culms 10 — 35 cm. 

 tall. The plants look like delicate 

 little trees with open crowns. The 

 silvery spikelets are closely clustered 

 at the tips of the branches. Dry 

 ground, mostly in the Atlantic and 

 Pacific coastal regions. Introduced 

 from Europe. April — July. 



Figure 181 



8a. Spikelets disarticulating above the glumes 9 



8b. Spikelets disarticulating below the glumes and falling entire. Fig. 

 182. 



' Trfsefum pennsylvanicum (L.) Beauv. 



Perennial; culms slender and 

 weak. 50—100 cm. tall; tufted. The 

 spikelets are very flat and fall 

 with about half of the pedicel at- 

 tached. Meadows, swamps, and 

 wet ground. May — June. 



TTisetum interruptum Buckl. has 

 similar spikelets but a dense, 

 spikehke panicle. Open dry 

 plains, Texas to Colorado and 

 Arizona. March — May. 



Figure 182 



97 



