303 



seqnently a fair percentage of tlie seeds are allowed to come to maturity. In the 

 very succulent Avliitc ovary the puncture made in laying an egg is usually seen easily 

 immediately after the ovipositor is witlidrawn, and a rather large droj) of clear sap 

 not infreiiuentl^^ exudes from it Avithin a short time. 



Having withdrawn the oviduct, in doing which she moves uj) so that h(^r head is 

 about level with the stigma., or even l>efore this organ is entirely freed, the moth 

 usually proceeds to pollination; hut it is not infrequent for two eggs to 1)6 laid 

 between each two visits to the stigma, and, owing to her peculiar alertness, she 

 a])pears to Ix^ even more easily frightened into omitting pollination than are the 

 other species of Pronuba. Standing with her head at about the height of the 

 stigma, with the short tongue i)rojecting out in front, she uncoils her long tentacles 

 from the compact mass of pollinia — which she carries similarly to the other Pronu- 

 bas — only that small x)art of her burden which adheres to the bases of the tentacles 

 being removed from it, and, raising her body on tiptoe, she very slowly saws the 

 tentacles back and forth across the top of the stigma, generally following one of the 

 three shallow grooves, and very carefully working their slender tips into the more 

 or less gummy exudation over the central depression. Sometimes the operation is 

 interrupted long enough to admit of the tentacles being coiled back against the 

 load of pollen and again extended; but the curious manner in which her head is 

 held back from the stigma as a rule prevents any of the main load from reaching 

 even the marginal papilhe. 



On first witnessing this operation, I was impressed by the much slower motion of 

 the moth than usual and the evident care which she took to run the ends of the ten- 

 tacles into the central depression of the stigma, which I then supposed to be solid ; 

 the subsequent discovery of the stylar canal, communicating with the ovarian cells, 

 showed that it is into this narrow passage that she so carefully guides the tips of 

 her tentacles with their modicum of j)ollen, and no doubt the abundant stigmatic 

 secretion serves not only to foster the development of the nascent pollen tubes after 

 pollination, but, wetting the tentacles, aids in the disintegration of her mass of pol- 

 linia. These, if really related to her work, would seem to have acquired their 

 coherent structure as a means of facilitating their collection, rather than as an 

 adaptation to their removal bodily from the anther to the stigma as is the case in 

 orchids and asclepiads, where, however, special means of secure attachment to the 

 insect accompany this aggregation of the pollen grains into a large mass. 



A farther iuterestiug fact connected with the pollination of this sx)ecies 

 is that Prof. Trelease discovered a purely black variety (which he 

 describes as aterrhna) of Fronuba maculata connected Avith the variety 

 (jraminifolia (Wood) of Yucca ichipplei, 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 move- 

 ments. 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, then quickly clambers upon the inner side of a filament, and, with the 

 tentacles extended over the pollinia, drags first one and then the other out of the 

 anther cells, pressing them together under the throat, and subsequently compacting 

 the mass together, much as i/KccaseUa 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 that the stamens are 

 often shaken quite violently, as I have before noted in the more nervous attemptsof 

 yuccasella. 



PRONUBA YUCCASELLA ON THE PACIFIC COAST. 



Of the tieshy-fruited Yuccas, among others, Prof. Trelease was able 

 to study Yiccca haccata Torrey, which is pollenized by Pronuba yucca- 



