198 THE NATURE AND WORK OF PLANTS 



composition ? Is it chiefly sand, clay, or rock ? Is 

 the rock limestone, granite, or quartz ? Is the soil 

 covered with a layer of fallen leaves, or has this been 

 destroyed ? 



It will next be of importance to determine the 

 trees which make up the larger members of the com- 

 munity. With regard to this point two kinds may be 

 distinguished : pure and mixed forests. A pure forest 

 shows but one kind and a mixed forest many kinds 

 of trees. What species is most abundant ? Are the 

 trees closely crowded together so as to completely 

 shade the ground, or are they wide apart, thus per- 

 mitting light to reach the ground and the growth of 

 many other plants ? Pure forests, made up of pines, 

 hemlocks, or beeches generally shade the ground so 

 completely as to make it impossible for undershrubs 

 to live. Oak, maple, and hickory forests are generally 

 open and have much underbrush. Make a map of the 

 forest, showing the facts in regard to the occurrence 

 of the different kinds of trees. The trees may be 

 evergreen, retaining the leaves throughout the winter, 

 or these may be cast in the autumn. 



Find the seedlings or young specimens of the trees, 

 and note whether they have found a foothold in 

 shaded or suuny places. Find a place where a tree 



