HOW TO KNOW THE GRASSES 



57b. Sheaths bearing conspicuous tufts of white hairs at their summits. 

 Fig. 241. 



SAND DROPSEED Sporoboius CTyptandrus (Torr.) Gray 



Perennial; tufted, the erect or spreading 

 culms 30 — 100 cm. long; panicles borne 

 at the apex of the culms and in the axils 

 of the upper sheaths. The tufts of straight 

 silky hairs on the flanges at the summits 

 of the sheaths are prominent. Sand drop- 

 seed is a rather important forage species 

 on coarse or sandy soil in the West. It 

 produces an abundance of fine, long-lived 

 seed, and will recover rapidly from the 

 effects of overgrazing. July — October. 



SpoTobolus giganteus Nash (GIANT 

 DROPSEED) resembles the above, but may 

 be distinguished by its large size, from 

 1 — 2 m. tall, and slightly larger spikelets, 

 2.5 — 3 mm. long. Sand plains, western 

 Oklahoma and Texas to Colorado and 

 Arizona. 



Figure 241 



58a. Panicle not more than twice as long as wide; leaf blades usually 



rolled. Fig. 242. 



ALKALI SACATON Sporoboius airoides Torr. 



Perennial; culms tough and rigid, in 

 large clumps; plants 50 — 100 cm. tall. The 

 large, open, dome-shaped panicles make 

 up half or more of the height of the plant. 

 The paleas of the florets often spHt as the 

 grain develops. The plants can grow on 

 very salty or alkaUne soil. Although the 

 herbage is tough, it is taken greedily by 

 livestock, probably because of the large 

 amount of salt in the tissues. Frequently, 

 minute salt crystals can be seen glisten- 

 ing on the leaf surfaces with a hand lens. 

 Plains and alkaH flats, often on heavy 

 clay soils. Jime — September. 



Figure 242 



128 



