52 



debris of all kinds, and is almost always devoid of any plant growth. 

 9. Andropogon furcatus. — The bunches of this grass, commonly 

 known as blue joint, resemble those of the smaller A. scoparius in 

 general habit, but are taller, 1.5-2.5 feet (4-8 dm.), and frequently 

 larger in diameter, three to four feet (8-12 dm.). The leaves are 

 larger, less densely aggregated, and without the tangle of dead leaves 

 among them. The flowering culms are three to five feet (10-15 dm.) 

 tall or even more, and seldom persist until the following summer. 

 Like A. scoparius, the bluejoint may also form rings by the death of 

 the center of the old bunches. These are five to seven feet (15-20 

 dm.) in diameter and without a conspicuous elevated center. 



Sorghastnini nutans and Paiiicum znrgatuiii (PL IV, Fig. 2) 

 form large bunches much resembling those of bluejoint. Calamovilfa 

 longifolia grows in patches with the individual culms one to six 

 inches (3-15 cm.) apart, forming dense clusters which resemble true 

 bunches. Bragrostis trichodes produces bunches closely resembling 

 those of Andropogon scoparius in general character, but without the 

 mass of dead lea\'es. The bunches of Panicnm pcrlonguni are very 

 regular, hemispherical in shape, and composed of a dense mass of 

 straight radiating leaves. In general appearance they resemble the 

 bunches of Koeleria cristala. Paspahnn sctaccuui and Bragrostis 

 pcctinacca send up several culms from a common center, on which 

 the leaves are most closely approximated near the base, thus forming a 

 loose irregular bunch. The loose open bunches of Care.v Mnhlcn- 

 bergii are especially characterized by their leafless, obliquely ascend- 

 ing stems. 



Since the bunch-grasses virtuall}- exclude other growth beneath 

 them, the secondaiy species are found upon the small areas of bare 

 sand between the bunches. They may be conveniently divided into 

 four ecological groups based upon their habits and structure. As in 

 most ecological classifications, these groups are not entirely distinct, 

 and some species are of doubtful position. To them may be given the 

 names perennials, mats, interstitials, and parasites. 



The members of the first group, the perennials, are generally very 

 deep-rooted, and frequently grow in tufts or bunches resembling those 

 of the bunch-grasses. The deep roots are a response to the conditions 

 of water supply, and the bushy habit is possibly correlated with the 

 generally xerophytic en\'ironment and exposure to the wind. Re- 

 sembling the bunch-grasses in habit, they are able to compete with 

 them for space, and may be found in the center of a patch of grass, 

 where they have persisted since the grass surrounded them. Their 



