Nov. i6. 1914 Revegetation of Range Lands 105 



In 1909 the seed-maturity period began eariier than in the two pre- 

 ceding seasons. In the case of mountain bunch-grass and a few other 

 species this difference amounted to as much as 10 days in the identical 

 situations observed in previous years. As with the production of flower 

 stalks, the latest period of seed maturity occurred in 1907. The seed of 

 vegetation on the cool and moister north slopes invariably matured later 

 than that on other exposures and on level land at the same altitude, the 

 difference amounting to a week or 10 days. Elevation is, of course, 

 influential in determining the time of seed maturity. Each increase of a 

 thousand feet, other conditions remaining the same, brings about an 

 approximate delay of a week. The chief factor in determining the time of 

 seed maturity, however, as well as the size of the seed crop, is the vigor 

 of the vegetation. Where the herbage had been grazed for several suc- 

 cessive seasons when green and the vitality of the vegetation thus low- 

 ered, no seed was produced, or else the period of maturity came so late 

 as to be seriously interfered with by frosts and low temperature. In 

 contrast to this, the seed-ripening period on yearlong protected lands and 

 on those not grazed until after seed maturity was much earlier and more 

 uniform, while the amount of seed produced was notably greater. 



On the unprotected range there was little difference in the time of 

 seed maturity from year to year. On both the yearlong protected range 

 and that grazed after seed maturity, however, the period came earlier 

 each successive season, in direct ratio with the increase in vigor of the 

 vegetation. 



The importance of keeping the vegetation thoroughly vigorous is 

 further exemplified by the clipping experiments. Where the herbage 

 had been removed monthly for three successive seasons, no seed was 

 developed in the fourth year when the plots remained undisturbed. On 

 the other hand, on the plots clipped annually after seed maturity the seed 

 crop was fully as large and matured at the same date as on lands from 

 which stock were excluded. 



The experiments show, therefore, that if the forage crop is left undis- 

 turbed until the seed has ripened, at which time the plants will have 

 ceased growing, it will produce as large and as early a seed crop the fol- 

 lowing season as will vegetation on range not grazed at all. Clearly 

 these facts are of the greatest importance in devising a system by which 

 the forage may be grazed without interfering with seed production. 



VIABILITY OK THIi SEED CROP 



The germinative power of the seed of the leading range plants was 

 determined, in order to ascertain what reproduction might be expected 

 under favorable conditions. In Table II, which gives the results of the 

 tests, the high-range and low-range plants are grouped separately. 



