THE GRAVEL-SLIDE COMMUNITY. 



81 



VI. THE GRAVEL-SLIDE COMMUNITY. 



A fine series of diverse habitats for investigation are found in the 

 mountains adjoining the plains. During August a detailed investiga- 

 tion was made of the roots of plants at an altitude of about 8,000 feet 

 in the Pike's Peak region of the Rocky Mountains. Here the soil is 

 composed of disintegrated granite, the degree of disintegration and 

 decomposition determining largely the type of plant community 

 occupying any particular area. The successional sequence and species 

 belonging to each community of the sere may be found in pubHcations 

 by Clements (1904, 1905). The first herbaceous plants to occupy the 

 new soils formed by the crumbling granite on the steep mountain slopes 

 are members of the gravel-sUde community (plate 23). The semibare 

 areas thus populated are so extensive and the fife conditions so unique 

 that a rather detailed study was made of the most important species. 



Krynitzkia vu'gata. — ^This striking plant has an erect, spike-like stem seldom 

 reaching a height greater than 8 to 12 inches in this habitat. It is a principal 

 species of the gravel-shde community. It has a tap-root 4 to 9 mm. in diam- 



FiG. 31. — Krynitzkia virgata. The heavy slanting line indicates the actual ground-line. 



