230 



THE FLOWER 



clover and the bumblebee was brought to light a few 

 years ago when the plant was first introduced into Aus- 

 tralia. It grew luxuriantly and blossomed 

 profusely, but would never set seed till the 

 bumblebee was introduced to keep it com- 

 pany. 



The most remarkable of these partnerships, 

 perhaps, yet observed by naturalists, is that 

 which exists between the little pronuba, or 

 yucca moth, and the flowering yuccas, of 

 which the bear's grass and Spanish bay- 

 453 . -Pod of onet of our 



yucca angustl 



fields and 



folia pierced by . 



the Pronuba roadsides are 



familiar ex- 

 amples. If any of these 

 plants grow in your neigh- 

 borhood, examine the pods 

 and observe that none of 

 them are perfect, but all 



. . 454. Moth resting on yucca blossom. 



show a constriction at or 



near the middle, such as is sometimes seen in the sides 

 of wormy plums and pears. This is caused 

 by the larvae of the moth, which, feed upon 

 the unripe seeds. If you will look under 

 the nodding perianth of a yucca blossom 

 (Fig. 454), you will see that the short sta- 

 mens are curved back from the pistil in 

 such a manner that under ordinary circum- 

 stances, not a grain of the pollen can fall 

 upon it except by the rarest accident. But 

 the yucca moth is a good farmer as well 

 as a provident mother, and as soon as she 

 455. Pronuba has deposited her eggs in the seed vessel, 

 takes care to provide a crop of food for her 

 offspring by gathering a ball of pollen in 



her antennae and deliberately plastering it over the stigma 



(Fig. 455). In this way she insures the perfecting of the 



pollinating pistil 



of yucca. 



