THE YUCCEAE. 125 



kept from shorter-tongued insects, is so closely applied 

 about the lower part of the ovary, as, apparently, to make 

 it impossible for any insect to reach the bottom of the 

 latter, with even a very slender tongue. Though the 

 actual pollination of this genus is yet to be observed, it is 

 effected by Pronuba yuccasella, at least in 8. Faxoniana, 

 in the flowers of which pollen-laden females of the moth 

 were discovered by my son and myself in April, 1902, and 

 the only explanation of the highly specialized tubular peri- 

 anth I can suggest is that, restricting the access of the 

 ovipositing moths to the upper half or two-thirds of the 

 ovary, it may limit the number of eggs that they can lay 

 in a given pistil, to the advantage of the plant. 



EXPLANATION OF PLATES. 



Unless otherwise stated, the illustrations are from pho- 

 tographs by the author. Where two illustrations occur on 

 a plate, the upper or left-hand is referred to first. 



Frontispiece to article. Samuela Carnerosana, in the Carneros Pass, 

 Mexico. 



Plate 1. 1, Hesperaloe parmflora, cultivated in San Antonio; 2, H. 

 jparviflora Engelmanni, cultivated at the Missouri Botanical Garden. 



Plate 2. Flowers of Hesperaloe parviflora Engelmanni, natural size. 

 from the Missouri Botanical Garden. 



Plate 3. Hesperaloe funifera, at Peyotes, Mex. 



Plate 4. 1, Hesperaloe funifera, capsules from Peyotes, natural size ; 

 2, Hesperoyucca Whipplei, capsules from Arrowhead Springs, Cal., natural 

 size. 



Plate 5. Hesperoyucca Whipplei, and its flowers, reduced, at the sum- 

 mit of the Cajon Pass, California. 



Plate 6. Clistoyucca arborescens, at Hesperia, California. 



Plate 7. Clistoyucca arborescens, flowers, reduced, and fruit, natural 

 size, at Hesperia, Cal. 



Plate 8. Yucca filamentosa, at Sanford, Fla., and flowers, natural size. 



Plate 9. Yucca filamentosa bracteata, cultivated at Brunswick, Ga. 



Plate 10. Yucca filamentosa concava, in sand dunes, Isle of Palms, 

 S. C. 



Plate 11. Yucca filamentosa media, cultivated in Tower Grove Park, 

 St. Louis. Photographed by P. T. Barnes. 



Plate 12. Partly grown fruit of Yuccas cultivated in the Missouri 



