298 Science of Plant Life 



coats which may cause them to remain dormant for long 

 periods. When planted, some of the seeds germinate the 

 first season, others the second, and some not until the third 

 or fourth year. This tends to insure some of the seedlings 

 favorable conditions for growth. All the seeds will genninate 

 the first season if the waterproof outer coat is ground off by 

 shaking the seeds with sharp sand. In tree nurseries seeds 

 are usually treated in this way, so as to insure the rapid and 

 uniform development of the seedlings. 



The conifer forests of North America. The greater part 

 of the forested area of this continent is occupied by conifers. 

 One of the striking characteristics of conifer forests is the fact 

 that extensive areas are often occupied by a single species. 

 In the Northern Evergreen Forest, which stretches from the 

 lower St. Lawrence basin to Alaska and extends southw^ard in 

 the Alleghanies to northern Alabama, the principal trees are 

 the white and black spruce, white pine, hemlock, jack pine, 

 balsam fir, tamarack, and arbor vitae. The spruces are the 

 principal source of the wood pulp used in the manufacture of 

 paper. The white pine formerly furnished the most durable 

 and most desirable lumber in the Eastern states, but the 

 supply of this lumber is now almost exhausted. 



In the Southeastern Evergreen Forest, which extends along 

 the coastal plain from New Jersey to Texas, the long-leafed 

 and short-leafed pines, the loblolly pine, the cypress, and the 

 red cedar are the most important timber trees. The long- 

 leafed pine is the source of rosin and turpentine, and with 

 other pines and the cypress it supplies much of the lumber 

 for interior finishings and other building purposes. Cypress 

 lumber is noted for its durabiUty in moist situations where 

 other lumber soon decays through the attacks of fungi. 



