86 OUR NATIONAL FORESTS 



ment Stations is grouped under such categories as 

 these: dendrological studies, forestation studies, 

 studies in forest influences, studies relating to forest 

 management, studies in forest protection, commer- 

 cial tree studies, and grazing studies. 



Dendrological Studies. Dendrological studies 

 include studies in tree distribution and wood identi- 

 fication. For each tree species growing in the 

 United States (and there are about 500 of them) it 

 is desirable to know its geographical distribution, 

 its commercial distribution, and its local distribu- 

 tion. The first of these deals with the entire range 

 of the tree by geographical divisions ; the second of 

 these with the distribution of those bodies of timber 

 that are of commercial quantity or size ; and the last 

 deals with the distribution of the tree by local di- 

 visions, such as lowlands, slopes, ridges, valleys, 

 plateaus, etc. This information is usually placed 

 on maps for permanent record. Observations by 

 Forest officers on the many National Forests are re- 

 corded by them and at the first opportunity sent to 

 Washington. Very often it happens that the range 

 of a species of tree is considerably extended and 

 that a tree is found growing in a locality where it 

 was never reported from before. The identifica- 



