HOW TO KNOW THE GRASSES 



13b. Nerves of lemmas glcxbrous, the callus with a tuft of long hairs; 

 plants with slender, elongated rhizomes. Fig. 50. 



BLOWOUT GRASS 



Rediieldia flexuosa (Thurb.) Vasey 



Perennial; culms 60 — 100 cm. tall; pani- 

 cles large, pyramidal; leaf blades smooth 

 and tough, elongated, inrolled. The spike- 

 lets when mature are fan-shaped, with con- 

 spicuous cottony tufts visible from the 

 side. Because of the numerous long, slen- 

 der rhizomes, blowout grass is able to 

 keep pace with the shifting sands and 

 eventually bind dunes into place. It is 

 an important sand-binding grass on sandy 

 plains from South Dakota to Oklahoma 

 and Arizona. August — October. 



Figure 50 



14a. Palea not fringed with long hairs; plants perennial 15 



14b. Palea fringed with long hairs on its upper half; plants annual, 

 with weak, shallow root systems. Fig. 51. 



Triplasis purpurea (Walt.) Chapm. 



Annual; tufted; culms 30 — 75 cm. long, 

 erect or spreading. In late season, the 

 herbage may become quite reddish. The 

 small terminal inflorescence usually pro- 

 trudes somewhat from the uppermost 

 sheath, but the axillary panicles are con- 

 cealed in the swollen sheaths and have 

 cleistogamous spikelets. Common on san- 

 dy lands. July — October. 



Figure 51 



Triplasis ameiicana Beauv. is a similar species of the southeastern 

 states. It is perennial and the lemmas have awns about as long as 

 the body. 



28 



