THE VOICE OF THE DESERT 



84 



only a few of the perhaps two hundred seeds which the 

 pod produces. From the standpoint of the yucca it is a very 

 good arrangement since the sacrifice of a few seeds is a 

 small price to pay for a very efficient job of fertilization. 

 The staggering question for anyone who has committed 

 himself to "explaining" nature is simply this : How on earth 

 was such a system of mutual cooperation for individual 

 ends ever worked out? 



Evidently the yucca and the }aicca moth came to their 

 mutual understanding a long time ago — certainly before 

 the plant genus had evolved the many species now flour- 

 ishing — because^ with the one exception previously men- 

 tioned, they all seem to be signatories to tlie agreement; 

 certainly, also, long enough ago for the Pronuba moth to 

 have itself evolved into at least several distinguishable spe- 

 cies, because those which visit certain yuccas are slightly 

 different from those which visit others. On tlie other hand, 

 moth and yucca have not always worked together, be- 

 cause the flower continues to secrete a nectar which now 

 merely attracts useless insects of various sorts and pre- 

 sumably it learned to do that at a time before Pronuba got 

 into the habit of paying a visit on business of her own for 

 which no honeyed inducement is necessary. 



Apparently, sometime during the millennia when the 

 two were engaged in a late phase of their evolution and 

 separating themselves into the different species of m^oth 

 and yucca, they must themselves have kept together. 

 "Wherever thou goest I go," said the moth, because, again 

 with the one single exception, w^iere a yucca is native, so is 

 a Pronuba. Attempt to grow the former outside its range 

 and it may flower very nicely. But "no moth, no seed" 

 seems to be the absolute rule. 



