LUTHER BURBANK 



and presently will eat their way out of the 

 ovary and fall to the ground, where they will bury 

 themselves for a season; coming forth as adult 

 moths in the succeeding summer, just at the time 

 when the yucca is flowering. 



Service for Service 



At first glance it is not obvious how the yucca 

 profits by this curious arrangement. 



But observation shows that the progeny of the 

 moth seldom or never consume all the yucca seeds 

 that are so conveniently stored about them. After 

 they have eaten their fill and have sought a new 

 shelter, enough yucca seeds remain to insure per- 

 petuation of the species. The progeny of the 

 moth have indeed taken toll of part of the crop 

 of yucca seeds in recompense for the services 

 performed by their mother. 



But, on the other hand, had not the moth paid 

 its visit, the flower would by no chance have been 

 fertilized at all. 



Here, then, is a case in which there is absolute 

 mutual dependence between a particular species 

 of insect and a particular species of plant. In the 

 desert regions it inhabits, the moth could find no 

 other place to deposit her eggs where food would 

 be assured her offspring; and in the burning desert 

 air, the stigma of the yucca, if not placed deep 

 within the tissues, could hardly endure exposure 



[200] 



