I02 Journal of Agricultural Research voi. m. no. 2 



25 and terminates about July 15. While climatic conditions have a 

 direct influence upon the time when growth begins, the length of the 

 growth-resumption period in a given locality is determined more by the 

 vigor of the vegetation than by anything else. Where year after year 

 the herbage has been removed prior to the time during which the nutri- 

 ents necessary for spring growth are stored in the roots, growth begins 

 several days later and vegetative development is strikingly less luxuriant 

 than in the case of plants of the same species which have not been sub- 

 jected to similar treatment. 



FLOWER-ST.^LK PRODUCTION 



Under ideal conditions flower stalks begin to appear from 10 days to 

 2 weeks after growth has started. The stalks make a vigorous height 

 growth, and there is a profusion of inflorescence, which is fertilized at 

 an early date. Actually, however, the period of flower-stalk production 

 is often retarded by cool temperatures and other cUmatic factors, so that 

 the time the stalks begin to show may vary in different portions of the 

 range as much as several days, similarly to the inception of growth. 

 Obviously the two are closely related, an early and prolific herbage pro- 

 duction being followed by an early and luxuriant flower-stalk develop- 

 ment, and a late, scanty growth of herbage by a correspondingly late 

 appearance of a few weak stalks. 



The vigor of the vegetation and consequently the time and abundance 

 of flower-stalk production are also strongly influenced by the way the 

 lands are grazed. Close cropping, coupled with successive trampling 

 prior to the full development of the plant, delays not only the flower- 

 stalk production, but also the maturing of the seed crop in subsequent 

 years. The period required for an overgrazed plant to regain its vigor 

 depends on the amount of injury received and the situation in which it 

 grows. Three seasons of protection from grazing are usually sufficient 

 for herbaceous vegetation to recover its vigor fully. 



To determine the actual difference in the time of flower-stalk pro- 

 duction on closely grazed, moderately grazed, and protected areas, as 

 well as the time required for overgrazed plants to recover their lost vigor, 

 observations were made during three successive seasons of mountain 

 bunch-grass areas grazed in different degrees, and on others completely 

 protected from stock. The range selected was at an elevation of 7,300 

 feet in the heart of the Hudsonian zone. The unprotected or open range 

 was grazed according to the usual practice, the forage crop being removed 

 early in August each year, prior to maturity. 



During the first year (1907) no difference was observed in the time 

 of flower-stalk production on the protected and open ranges, since the 

 vegetation on both had previously been weakened through grazing. In 

 1908 and 1909, however, there was a notable difference in flower-stalk 

 production, as shown in Table I and Plate XV, figure i. 



