THE VOICE OF THE DESERT 



146 



ers won't sprout until the following spring, and the seeds 

 of midsummer plants won't sprout until the following 

 summer. Yet in neither case is it merely a matter of how 

 long they must remain dormant. The spring group waits 

 until it is wet but cool, the summer group until it is wet 

 and warm. Elaborate experiments carried on some years 

 ago at the now disbanded Carnegie Desert Laboratory es- 

 tablished not only the general fact but the critical tempera- 

 tures. For most of the winter ephemerals the optimum 

 temperature for germination is 60 to 65 degrees, for the 

 summer ephemerals between 80 and 90. Most will do 

 fairly well within a range of 5 to 8 degrees above or 

 below the optimum. That leaves a margin of about 5 to 10 

 degrees between the highest temperature at which the 

 seeds of the spring flowers will grow and the lowest ac- 

 ceptable to the summer ones. It seems a narrow margin of 

 safety where so much is at stake. But it is not too narrow 

 to work very successfully. No feature of the desert is more 

 striking than the spring carpet of flowers which covers 

 large areas with thousands of blossoms. Yet the seed from 

 which each sprang had to resist, during the whole previous 

 summer, any temptation to germinate when the ground 

 was moist and (one would have supposed) pleasantly 

 warm. It had to wait until moisture with coolness proved 

 that spring, not summer, had come. 



It happens that I am writing this chapter in midwinter, 

 and on the table beside me are a number of containers 

 which represent my successes and my failures in various 

 attempts to deceive desert seeds into believing that the 

 time for their resurrection is right. One of the most con- 



