58 HOUGH'S AMERICAN WOODS. 



Scientists have found that the Tree Yucca is preeminently depend- 

 ent upon the insect world for the fertilization of its flo^ ers, and this is 

 accomplished in a very remarkable way. The insect in this case 

 plainly sets about its task with the fertilization of the ovnle its ob- 

 jective point, instead of that being an incidental consequence of the 

 visit of the insect which is generally the case as far as the insect is 

 concerned. With this plant the female nocturnal moth (Pronuba 

 synthetica, Riley) gathers pollen from one flower and carrying it to 

 another places it on the stigma there, depositing its egg in the pistil of 

 the flower at the same visit. Her object in thus fertilizing the flower 

 is purely maternal that the ovules may develope and furnish food for 

 her offspring, which requires, however, but a small portion of the 

 quantity resulting from her labors and the surplus goes to perpetuate 

 the species. 



For more detailed information regarding this interesting fertilization 

 of the Yucca, see The Silva of North America, by Charles Sprague 

 Sargent, vol. X, pp. 1 and 2, note, where other references are also cited. 



