By permisson of U. 8. Dept. of Agriculture. 
Fig. 49. A hill farm on which a heath-like vezetation — largely sweet 
fern — is invading the grassland stage. It is in such cases that the soil structure 
has become degraded. 
By permission of U. 8S. Dept. of Agriculture. 
Fie. 50. Pasture land in southern New York reverting to forest. The 
grassland is being invaded by ferns, small shrubs and the advance guard of 
forest trees. 
i ee 
