j8 — THE P SYCHOLOG Y 



(ilaiits and tlio soil. Some plants flourish best in sandy soil, and are likely to crowd 

 otliers out ofsueh soil, thougli these others mig^ht be able to grow there, if not in' 

 competition with those natives, as they may be called. Other plants grow in water, 

 and cannot possibly live on dry land. Others grow in swamps, others in shady 

 woods, some in sunny places,, and some prefer m-ineral soil. Thus, of trees, 

 evergreens j>refer sandy or gravelly soil, wliile the hardwood trees, oak, maple, 

 beech, need a heavier soil, clay loam. Willow and sycamore grow beside flowing 

 streams, and tamarack in- cold, wet soils. The study of these groups of tree* 

 may be carried on \oy sevei^al 3'earsr 



Modern botany places great stress upon the study of the adaptation of plants- 

 to environment, which is known as ecology. Plants are found to grow in societies, 

 according to the nature of the soil, moisture and climate. Thus, we have peat 

 bog societies, swanvp societies, forest societies^ desert societies, fence-corner,, 

 and roadside societies. 



Four great societies are now recognized : (r) Water plants, i. e., those which 

 grow where water is abmidant, (Hydrophytes); (2) Drought plants, i. e., those 

 which grow in extremely dry soil, and in a dry atmosphere, (Xerophytes) ; (3) 

 Plants that grow where there is a medium water supply, (Mesophytes.); (4) Plants 

 that grow in soil which contains a large amount of mineral matter, (Halophytes), 



