624 



BOTANY 



the Southern Atlantic states, and common in gardens. Most species 

 of Yucca depend for their pollination upon a small nocturnal moth of 

 the genus Pronuba. This moth deposits its eggs within the ovary 

 of the Yucca, and the larvae feed upon the young seeds. In order 

 that the flower may be fertilized, and the ovules developed into the 

 seeds necessary to nourish the larvae, the moth deliberately collects 

 a quantity of pollen, which it pushes into the cavity at the apex of 

 the stigma, thus insuring the fertilization of the ovules. In most 

 species of Yucca this is absolutely necessary in order that seeds may 

 be formed, and if the insect is absent the flowers will all remain 

 sterile. The larva of the Pronuba does not destroy all the seeds, a 

 considerable number remaining uninjured in the ripe capsule. 



FIG. 492. Ribes speciosum. A characteristic humming-bird flower. 



Ornithophily 



In America the humming-birds are important agents in pollinating 

 many flowers, this being especially the case in tropical America, 

 where the number of species of humming-birds is very great, and 

 many flowers are especially fitted to their visits. In the Old World 



