{Caltha palustris). This classification has been used advantageously 

 in analyzing many plant communities (see the table below). 



Growth-form (phenotypic-form) refers to the development of 

 plants of the same species under different environmental condi- 

 tions. In abandoned fields in the Great Plains, Russian thistle 

 {Salsola kali) may be 2 ft high, while in adjacent grasslands the 

 tallest plants are only an inch or two in height because of their 

 inability to compete with the perennial grasses. The growth-form 

 of a species may also vary greatly within a single stand because 

 of differences in microhabitats. Under heavy grazing, perennial 

 rhizome grasses become smaller, more prostrate, and form a short, 

 dense turf; while bunch grasses become reduced in size, with 

 fewer and finer stems and leaves per plant, and with the clumps 

 sometimes broken into smaller, separated tufts. As a consequence, 

 in some grasslands the growth-form has been considered a more 

 reliable indicator of grazing use than cover. 



Sociability (Gregariousness) 



Sociability refers to the proximity of plants or shoots to one an- 

 other. It is dependent upon the life-form and vigor of the plants, 

 habitat conditions, and competitive and other relations between 

 individuals. The Braun-Blanquet scale, ^^ given below, for rating 

 sociability of species, has been widely used in analyzing veg- 

 etation. 



Class 1 : Shoots growing singly 



Class 2: Small groups of plants such as Chenopodium spp., or 



scattered tufts, such as Aristida spp. (Figure 2-2) 

 Class 3: Small, scattered patches or cushions, e.g., patches of 



gramagrass or buffalograss, or large clumps of prickly 



pear cactus (Figure 1-4) 



96 • The Commimxmity 



