18 BULLETIN 545, U. S. DEPARTMENT OF AGRICULTURE. 



In the region studied this species has a wide distribution. It 

 occurs most abundantly and grows most luxuriantly in the Canadian 

 zone, though it is met with in a variety of situations in both the upper 

 and lower contiguous zones. In fact, the tendency of slender hair 

 grass to adjust itself to various sites is a marked characteristic. In 

 the well-aerated, finely disintegrated, basaltic soil of the plateaus in 

 the Hudsonian zone this species does not wilt notably until the 

 water content of the soil falls to between 8.5 and 10.0 per cent — a 

 relatively low figure. On the other hand, simultaneous drought tests 

 conducted in soils rich in organic matter, and where the plant had 

 had access to a high per cent of soil water at all times, resulted in 

 destructive wilting of the plant when the soil-water content was as 

 high as 15 per cent. In moist situations a meager root system is 

 developed, and on dry sites, while the root rarely penetrates deeply 

 into the soil, it spreads over corsiderable surface. 



The flower stalks begin to appear about July 10 in the drier situa- 

 tions, and a week or so later in moist places. By August 1 the 

 majority have put in their appearance. Mature seeds are found as 

 early as August 5, while the bulk of the seed crop is matured by 

 August 25. The tests made for seed vitality were confined to the 

 year 1909, and showed an average of 41.5 per cent. On lower ranges 

 somewhat higher figures were obtained, 56.5 being the maximum. 



The grazing value of this plant is relatively low, and in this respect 

 it does not compare favorably with tufted hair grass. Owing to its 

 shallow roots the plant is frequently pulled up. Sheep grazing on 

 this plant, especially early in the season when the soil contains a 

 high per cent of moisture and the roots are readily pulled out, start 

 masticating the leaf blades, but usually expel them when they fird 

 that roots and clinging dirt form the dessert to their diet. After a 

 few experiences of this kind they crop it but little. Since the tussock 

 is small, horses often pull up the entire tuft, and after eliminating the 

 greater part of the clingirg dirt by shaking it vigorously and rubbing 

 it upon the ground, sometimes devour the plant. After about 

 August 15 the leaves become air dried, and slender hair grass is then 

 disregarded as a forage plant by all classes of stock. 



Another species known as black hair-grass (D. atropurpurea) occurs 

 in scattered stand in open situations throughout the Hudsonian zone. 

 Being restricted to high elevations (it rarely occurs below 6,500 feet), 

 the flower stalks are not seen until July 15 and they continue to be 

 produced until about August 25. No seed is matured until about 

 September 1 and very little fertile seed is developed even in most 

 favorable seasons. Reproduction takes place vegetatively by means 

 of offshoots arising from root stocks. 



