ADJUSTMENT OF ORGANISMS TO ENVIRONMENT 373 



hazel and mandrake and moss, and in the soil there is 

 likewise a more or less definite arrangement of the roots in 

 strata, less easily observed because hidden, but probably as 

 real, because supported by the stratification of the soil. 

 The smallest herbs usually root in the top soil, the majority 

 of shrubs in the subsoil, while many of the trees strike root 

 far deeper. By these means the resources of both light and 

 soil are more fully utilized and a more abundant and varied 

 flora is maintained. 



The dominant plants are usually of erect habit of growth, 

 conforming more or less closely to some of the commoner 

 typical forms shown in the accompanying diagram (fig. 217); 



FIG. 217. Diagrams of growth habit in plants, a, rosette; b, scape; c 

 wand; d, bush, <?; crown; /, climbing; g, twining; fc, trailing. 



but growth habit varies with crowding and with the conse- 

 quent restriction of the light. 



Study 45. Woodla'nd plant society. 



Field study. Select a bit of woods that has retained 

 natural conditions, at least as natural as possible. Lay 

 out a small area, a strip a few rods long, containing some 

 diversity of conditions, for a detailed study of its green 

 plant population. It must needs be a small area in order 

 that all members may be examined. In order to determine 

 the normal characteristics of some of the larger or rarer 

 species it may be necessary to extend observation of these 

 over a wider area. 



