ECADS. 89 



and which likewise run in all directions, they form a tangle which is exceed- 

 ingly efficient in preventing soil movement. The rhizomes are from 2 to 5 

 mm. in diameter, tipped with long, sharp-pointed buds. The roots are 1 to 4 

 mm. thick. They spread laterally 4 or 5 feet or more or penetrate downward 

 to a working depth of about 5.5 feet. They were abundant still at 6 feet, 

 while the deepest were found 0.8 foot lower. Throughout their entire course 

 they are abundantly furnished with well-branched laterals, except the 4 to 

 6 inches near the growing tips of younger roots, the whole forming a very 

 efficient absorbing system. 



Calamovilfa longifolia. — This tall, coarse sand-reed, while of no great forage 

 value, is an efficient sand-binder, and, like the preceding species, is important 

 in holding the sand and thus permitting the entry of more stable vegetation. 

 Not infrequently it invades with Redfieldia and other pioneers, but normally 

 occurs somewhat later in the succession along with Andropogon hallii. 



In the dunes at Colorado Springs the roots and rhizomes of this species 

 formed mats in the loose sand to depths of 2.8 feet. Many of the deeper roots 

 penetrate more or less vertically downward to a maximum depth of 5 feet; 

 but in addition to these there are abundant laterally spreading surface roots. 



This species was thoroughly examined at Central City. The plants were 

 better developed, covered a larger local territory, and had apparently been in 

 possession of the area for a much longer period (plate 10, b). The roots 

 reached a maximum depth of 6.5 feet and many of them were found at a depth 

 of 6 feet. As shown in plate 17, c, the tough, wiry, much-branched, and 

 matted rhizomes were intermixed with the roots to a depth of about 2.5 feet. 

 They are 2 to 4 mm. in diameter, clothed with long scales, and tipped with 

 long, hard, sharp-pointed buds. Some of the rhizomes, which were probably 

 at one time more superficial, were buried deeply in the shifting sand. The 

 multitudes of tough, wiry, deeply penetrating roots may be seen in the bisect 

 (plate 12, a) , where the sand has been removed to a horizontal distance of about 

 2 inches. The great tenacity with which the abundant, short, but repeatedly 

 branched laterals cling to the moist sand is clearly shown. There is only a small 

 portion of the root system shown in the bisect, but at a depth of 3 to 4 feet. 

 Where the grasses were at all thick, they held the trench-wall so well that little 

 danger from caving was experienced. 



At Haigler, in southwestern Nebraska, this species, with Andropogon hallii, 

 was excavated in an old road in mixed prairie. The surface soil was very 

 compact and hard in the first and second feet, but below this depth it was 

 easily removed. It was quite moist to the maximum depth of the trench, 

 about 11 feet. Calamovilfa roots were abundant to a depth of 8 feet. Some 

 reached a maximum extent of 10 feet. 



Finally, a further examination of the root penetration of the sand-reed was 

 made in the sandhills at Seneca, Nebraska, while excavating Ceanothus ovatus 

 (p. 57). Here the roots were found to reach a working depth of about 8 feet, 

 the longest ending in the moist sand nearly a foot deeper. 



Andropogon hallii. — This coarse, tall, yellowish-green grass occurs through- 

 out the sandhills, where, like A. scoparius, it is a dominant in the bunchgrass 

 subclimax. It forms close open bunches, with only a few characteristic large 

 stems, 3 to 6 feet tall. Plants of this species have been excavated on a par- 

 tially captured sand-dune southeast of Colorado Springs. Here it was found 

 to possess a rather shallow, copiously branched, but only moderately deep root 

 system. The lateral spread of the roots was 1.5 to 3 feet, while the maximum 

 depth of root penetration was only 2.3 feet. 



