48 BULLETIN 201, U. S. DEPARTMENT OF AGRICULTURE. 



SPOROBOLUS WRIGHTII Scribn. 



Sporobolus wrightii is the "sacaton" of the Mexicans, and it is confined to the 

 southwestern United States and Mexico. In former times it was a beautiful, charac- 

 teristic species of the river bottoms of the Southwest, forming dense growths 6 and 

 even 8 feet in height, through which it was difficult to ride on horseback. At the 

 present time there are but faint traces of this magnificent growth left. Some notion 

 of its habit of growth can be obtained from Plate I in Bulletin No. 4 of the Bureau 

 of Plant Industry, United States Department of Agriculture. Like Sporobolus 

 airoides, it has two distinct habits of growth, depending upon the location in which 

 it is found and the treatment which it receives. As near as can be judged, it made 

 a quite uniform stand oxex portions of the Santa Cruz bottoms in southern Arizona in 

 early days, but of late years it grows almost invariably in large tussocks and at present 

 there is very little of it left. In the valley east of the Baboquivari Mountains in 

 Arizona, we have a fine illustration of the effect of overgrazing on this grass; likewise, 

 a good illustration of its importance in preventing erosion. There are here pastures 

 which were formerly covered with a tall, smooth, uniform growth of saccaton. The 

 grass is now in huge bunches and this bunched condition is directly traceable to 

 paths cut in every direction by cattle. Invariably, when this species is grazed this 

 condition is produced, until the tussocks are often a foot in height. Of course, when 

 the grazing is carried to sufficient excess, one or more of these paths become cut to a 

 sufficient depth in the center of the valley to carry off the water very rapidly. Side 

 branches form and the tussocks are left high in the air, receiving but scant moisture. 

 Under this condition they soon die, and a great deal of the bottom land in southern 

 Arizona is to-day in this condition. In many places the tussocks have disintegrated 

 and disappeared altogether. (PI. VIII, fig. 1.) 



No. 8400 was collected near Green, Tex. , August 14, 1906. The sample was collected 

 in full blossom, the entire plant being green except the lower leaves, which were 

 dead and dry. It was cut 4 inches high. Its percentage of moisture was 8.59. Other 

 constituents (on a water-free basis) were as follows: Ash, 8.53; ether extract. 1.70; 

 crude fiber, 32.27; nitrogen-free extract, 47.93; protein, 9.57; pentosans, 25.89. 



STIPA COMATA T. and R. 



Stipa comata is a coarse species of needle grass of the western Plains region, where it 

 replaces the more eastern S. spartea. The pasturage and hay produced by it are 

 both of medium quality, but when found in hay meadows it is difficult to cut the grass 

 at exactly the proper time for the best quality of hay. The sharp-pointed fruits of 

 this grass sometimes injure stock to some extent. On this account, cutting the grass 

 after the seeds have fallen has been recommended. At this stage, however, it has 

 deteriorated somewhat in value and, inasmuch as it matures earlier than the other 

 prairie grasses, it can not be cut before the seeds have become old enough to be 

 injurious. Sheep grazing upon the prairies are sometimes injured by having the 

 seeds of this grass work into the fleece. Mowing, close grazing, or the removal of the 

 flocks from the localities where the plant grows at the time it is maturing its seed are 

 the remedies which have been suggested. Fortunately, the seeds drop to the ground 

 very soon after they mature and cause no further annoyance. 



No. 8824 was collected at Williston, N. Dak., August 11, 1907. The culms of the 

 sample wore all dead and dry and the seeds had fallen, with the exception of those 

 included in the expanded sheath. It was cut at the surface of the ground. 



