PREFATORY NOTE. 
Early in its administration of the National Forests the Forest 
Service was confronted with the problem of restoring the vegetation 
on many areas on which the natural ground cover had been com- 
pletely or partially wiped out by destructive overgrazing before the 
areas were included in National Forests. In order to secure the 
fundamental information on which beneficial changes in the prac- 
tice of grazing on such areas might be based the Forest Service 
joined the Bureau of Plant Industry in 1907 in a cooperative project 
of grazing investigations. Several important reports have been pub- 
lished, embodying the results of these various field studies, and the 
changes that have been made in the administration of grazing on 
the National Forests in accordance with the results of the investiga- 
tions have brought about conspicuous improvement in the ground 
cover, great advance in the protection of watersheds, and important 
increase in the number and quality of stock grazed. A part of the 
original plan of investigation was to make a detailed study of the life 
history of each important grazing plant for the special purpose of 
determining its reproductive season, from the sending up of the flower 
stalk to the maturing of the seed, and the period necessary to enable 
the new seedlings to reach a size and vigor sufficient to withstand 
moderate trampling by stock. In the course of these studies a very 
large amount of detailed information about the important grazing 
plants was acquired which could not be used in the more general 
reports already published. In the paper now presented for publica- 
tion a portion of this detailed information is given, in a form suited 
to the needs of forest officers and of stock owners who desire to 
familiarize themselves with the habits and requirements of the 
plants upon which their animals subsist. Such knowledge is neces- 
sary to the highest success in their business just as a knowledge of 
the habits and requirements of cultivated plants is necessary to the 
highest success in the business of the farmer. For the first time in 
the history of grazmg-plant literature the information needed to 
accomplish this result has been acquired and presented for public uso. 
Frederick V. Coville, 
Botanist, Bureau of Plant Industry. 
