PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 275 



was early applied to the region. The slightly pale green plants 

 are densely tufted into bunches from 1 to 4 inches in diameter, 

 and, while the numerous setaceous leaf blades are mostly basal 

 and about 12 inches high, the stems which bear flowers reach a 

 height of 12 to 18 inches. The whole plant dries out considerably 

 by the middle of July, but the autumn rains revive it, and it is 

 green throughout the rest of the year. 



Festuca ovina has a great mass of jet black roots which occupy 

 the soil thoroughly from the surface to a depth of about 18 inches, 

 below which depth relatively few roots extend. None of the 

 roots are over one millimeter in diameter. They branch pro- 

 fusely to the third order mostly, and the laterals are usually 

 less than an inch in length. This branching continues to the 

 very tip, and there the laterals are usually longer. Twenty- 

 two plants were examined. The longest root found was 3 feet 

 and 3 inches, the average length 2 feet and 1.5 inches for the 

 deepest roots, but the great bulk of roots were less than 18 inches 

 long. All the plants examined were on a southwest slope. 



Poa sandbergii (Fig. 11) 



Sandberg's Poa is one of the earliest plants to gain a foothold 

 upon the thin rocky soil of the scab-lands, and along the rim- 

 rock. It grows in small tufts usually only from 0.5 to 1.5 inches 

 wide, puts out new roots when the fall rains begin, grows through- 

 out the winter and spring, and evades drought by flowering late 

 in May or in early June, and remaining dormant the rest of the 

 growing season. On the prairies it is an interstitial plant, often 

 as many as 30-40 small tufts occurring in a single square meter 

 on the dry south slopes. 



Poa has smaller roots than Festuca ovina ingrata, they are 

 more profusely branched, and the fine laterals which are short 

 (usually less than 1 inch) are more numerous, smaller, and much 

 more branched. The creamy-white roots spread laterally 3 to 

 5 inches and occupy thoroughly the first few inches of soil, 

 relatively few extending below a depth of 8 inches, and none were 

 found beyond 13 inches. The root branches are longer and more 



