476 GENERAL MORPHOLOGY OF PLANTS 



Very few of the other conifers can develop effective coppice. 

 They are dependent on the seed for natural regeneration. On 

 the other hand, broad-leaved trees develop abundant coppice, 

 and in this respect have the advantage over conifers, which are not 

 shade-endurers or do not develop coppice. Broad-leaved trees 

 are limited, however, in their competition with conifers on thin, 

 sandy soil, and in cold regions, because many species of the 

 latter can grow with a low sum total of heat. 



647. Protection of forests. The fact that forests have an 

 important influence in regulating the movement and disposal of 

 rainfall has led the National Government and several State 

 Governments to adopt forest policies and to set apart certain 

 forest areas as reservations, especially in mountainous districts, 

 where lumbering is prohibited by law and efforts made to regen- 

 erate the forests where necessary and protect them from fire. 

 The value of these forest reservations is, first, the protection of 

 game and other wild animals; second, holding in reserve water- 

 storage for power, as well as for city supplies; third, the pro- 

 tection of the valleys and lowlands from destructive floods; 

 fourth, the providing healthful resorts where people find rest 

 from the busy and exacting professional and business lives. 

 When the principles of forestry are better understood by the 

 people the reservations will probably be cropped and regenerated 

 according to some suitable system which will not lessen their 

 value for the purposes for which they were first set apart, and 

 at the same time will yield the state a revenue sufficient to more 

 than pay for the cost of management, and also will tend to keep 

 within reasonable bounds the prices of building materials. 



OTHER PLANT SOCIETIES. 



648. The prairie and plains societies. These are to be 

 found in the grassland region. In the prairies, " meadows " are 

 formed in the lower ground near river courses where there is 

 greater moisture in soil. The grasses here are principally 

 " sod-formers " which have creeping underground stems which 

 may together, forming a dense sod. On the higher and drier 



