Black Vdi-'Klij of Pv'niuha viaculatn. 45 



A further interesting fact connected with the pollination of 

 this species is that Professor Trelease discovered a jjureh' hlack 

 variety (which he describes as aterrima) of Proniiba macidnta con- 

 nected with the variety r/raminifolia (\\'ood) of Yacca whipplei, 

 common in San Bernardino county. The actions of this black 

 variety are similar to those of the typical form, and it is also 

 diurnal rather than nocturnal in its movements. The method 

 of gathering the pollen mass is thus described : 



"Flying into a flower, the moth runs about the bases of the stamens 

 after the manner of other species, tlien quickly clambers upon the inner 

 side of a filament, and, with the tentacles extended over the pollinia, 

 drags first one and then the otlier out of the anther cells, pressing them 

 together under the throat, and subsecpiently compacting the mass to- 

 gether, much as yiiccasella does the powdery pollen of other Yuccas, so 

 that the ball finally consists of as many as ten or a dozen pollinia. So 

 quick and energetic are the motions by which the pollinia are removed 

 tiiat the stamens are often shaken quite violently, as I have before noted 

 in the more nervous attempts of yuccasellay 



Pronub.\ yucoasklla on the Pacific Coast. 



Of the fleshy fruited Yuccas Professor Trelease was able to 

 stud}^, among others, yiuxa baccata Torrey, which is pollinized 

 by Pronuha yuccasella. While he was not able to observe the acts 

 of pollination, all the circumstances and the facts which he ob- 

 tained would indicate that it is })recisely the same as described 

 for other species of Yucca that are fertilized by tiiis moth, and 

 the fertilized flowers show " conclusively that the pollen is thrust 

 well into the stigmatal canal,'' or in some cases ap{)arently even 

 into "the to[) of the ovarian cells, which, owing to the short 

 style and the deep stiginatic notches, they [the moths] can reach 

 easily with their long maxillary tentacles." The moths taken 

 from flowers at Cabazon and San Diego are somewhat above 

 the average in size, with the horny and chitinous parts somewhat 

 darker than in tlie tyi)ical form, l)ut specimens which he sent 

 me cannot be considered to have even varietal diftcrences, and 

 find their counterparts in my cal>inet in s})ecimens from Dakota 

 a,nd Colorado. 



Yuccd riiplcola Sclieele, of southern Texas, and Y. elala Engelm., 

 extending from southern Texas to southern Arizona, are both 

 pollinated by Proaiaha yuccasella^ as Professor Trelease ascer- 

 tained. 



