THE RESEEDING OF DEPLETED GRAZING LANDS. 21 



to show distress for lack of water, was killed mainly during* the sev- 

 enth week of growth. As evinced by its repeated wilting during the 

 warmer part of the day, timothy showed a more serious condition 

 than brome grass, which, as stated, was more deeply rooted than 

 timothy. During the latter part of the eighth week all the timothy 

 plants were killed, while some few brome-grass seedlings persisted 

 until the end of the tenth week. During this entire 10-week period 

 no precipitation, aside from that accumulated in the form of dew, 

 was received. Meanwhile, the minimum soil water content varied 

 from 4 to 9 per cent. A soil moisture content of 4 per cent marked 

 the lower moisture limits at which these plants could exist in the 

 habitat in question. 



A comparison of the time and degree of wilting of the various 

 species and their ability to recover from wilting further substan- 

 tiates the above classification as to moisture requirements. The 

 species which are able to recover from one wilting to another 

 may tide over the serious drought period, which may be broken at 

 any time* by the necessary precipitation. The time of recovery and 

 subsequent vigor varied with the different species. During the fore 

 part of the drought period all species usually began to recuperate 

 between about 4 and 7 o'clock p. m. each day. As the season advanced 

 the time of wilting among the species became notably prolonged and 

 more irregular. The more deeply rooted plants, smooth brome grass 

 and timothy, during the first few weeks varied but slightly in the 

 time during which wilting began, while redtop and Kentucky blue 

 grass would in many cases become limp two hours earlier and would 

 not recover from this condition for several hours after deeper-rooted 

 species had resumed the normal condition. 



There is no doubt that the ability of a plant to recover from wilt- 

 ing when in a soil of low water content depends upon the vigor of 

 the species, which, in turn, is largely determined by the depth of the 

 root system by means of which the moisture is secured. Each time 

 during wilting the root hairs in contact with the drier soil particles 

 are doubtless killed, and the gradual elimination of these moisture-ab- 

 sorbing surfaces results in earlier and more severe wilting each day 

 and finally, through the destruction of most of the root hairs, brings 

 death to the plant. 



RELATION OF ALTITUDE TO RESEEDING. 



The uppermost limits at which seeding was found to yield good 

 returns and the comparative yields at different elevations may best 

 be shown by comparative measurements of the average height 

 growth, density of stand, amount of seed yield, time of the flower 

 stalk production and seed maturity, and the viability of the seed 

 crop of the three closely studied species, timothy, Kentucky blue 

 grass, and redtop. The areas compared are as similar as could be 



