RANGE IMPROVEMENT BY DEFERRED GRAZING. 5 



flower stalks means that the seed has sufficient time to develop and 

 mature before low temperature comes in the autumn. In addition, 

 the earlier the flower stalks are produced the greater is their number 

 and luxuriance. 



The time of seed maturity varies to a certain extent with the time 

 of flower-stalk production, but to a less noticeable degree. Both tem- 

 perature and moisture conditions in a grazing region are more uni- 

 form after the time that flower stalks are sent up than before, 

 consequently the development of the vigorous plants is more uniform 

 with the advance of the season than during the spring period. In 

 the case of plants weakened by continuous removal of the herbage 

 during the early part of the season, the time of seed maturity is 

 delayed in proportion to the decrease in vigor. If the plant is 

 greatly weakened, no seed whatever is produced. Delay in seed 

 production may result in either very scant or actually no reproduc- 

 tion, for if the seed is to be fertile it must mature before prolonged 

 low temperatures or killing frosts occur. On the higher ranges 

 these may come at any time after August 20. The big struggle of 

 the vegetation is to mature its seed during a short and none too favor- 

 able period before the appearance of low temperatures and frost, and 

 to do this it must be kept in a high state of vigor. Added to the 

 other unfavorable conditions is the fact that the fertility of seed pro- 

 duced from even the most vigorous plants, especially on the higher 

 ranges, is comparatively low. 



A good example of the relation of plant vigor to the production of 

 fertile seed is found in the case of mountain bunch grass (Festuca 

 viridula), which furnishes a large part of the forage between eleva- 

 tions of 6,500 and 8,000 feet in the mountains of northeastern Oregon. 

 At the time of the grazing study there were found, under the same 

 conditions, all stages of plant vitality, from the final one of deple- 

 tion through starvation to the most vigorous growth. In the case of 

 uninjured plants the flower stalks invariably began to show about 15 

 days after growth had started, and from 6 to 15 were produced from 

 average-sized tufts. In contrast to this, the weakest individuals 

 developed no flower stalks, while those less seriously weakened pro- 

 duced none for a month or 6 weeks after growth had begun. Even 

 then the number sent up was invariably small, three being the aver- 

 age, and with a height but little more than half that of the stalks 

 produced early in the season by strong plants. This marked con- 

 trast in herbage and flower-stalk production between the weak and 

 strong vegetation is shown in Plate I. 



The strong and the weak plants exhibited similar differences in 

 the case of seed production. The most vigorous plants produced a 

 large and early seed crop; those of average vigor developed a much 



