' Pollination of other Species of Yucca. 95 



thick and leathery petals, but very al)normal in the Lepidoptera. 

 In fact, this species strongly recalls in its general aspect some of 

 the saw-flies belonging to the genus Dolorus, the resemblance 

 lieing heightened by the rather conspicuous, cenchri-likc spots, 

 and In' the conspicuous division between thorax and abdomen. 

 It also strikingly recalls some of the Neuroptera, as Sialis infninnta. 



Now these resemblances to insects of different Orders and to 

 families which are generally conceded to be of low type within 

 their Order, cannot possibl}^ be mimetic, as there can l)e no eon- 

 ceiva]:)le cause, purpose, or advantage in the mimicry. It is also 

 impossible to account for these resemblances upon any i)resent 

 genetic connection. Yet we are hardl}^ justified in disi)Osing of 

 them as merely accidental and without meaning. They suggest 

 a possiljle synthesism in the past, when types were less special- 

 ized and present Orders had not become so well differentiated. 



Yucca ivhipplei, which occurs in southern California, has flowers 

 distinguished by their relatively long and stout stamens, the 

 pollen of which is copious and glutinous, not to say mucilag- 

 inous, and a short, contracted style, with the stigma, however, 

 expanded and covered with sticky threads. It is pollinized by 

 Pronuhn muculata Riley, which, as already shown^ has a tongue 

 modified into an accessory pollen-gathering organ. If any 

 species of Yucca would seem not to need a special insect for pol- 

 lination, Yurcn u-Jiipplei is that species ; for the long stamens, the 

 sticky and abundant pollen, and the peltate, hairy stigma would 

 all seem to facilitate ordinary pollination. Nevertheless, the 

 very restricted style would seem to be purposely developed to 

 counteract these other facilities, and we find a Pronuba asso- 

 ciated with it, with a remarkably modified tongue, and with the 

 maxillary tentacles very long and attenuated at the tip — struct- 

 ures which doubtless enable the moth to perform the act t)f pol- 

 lination. 1 have never been able to ol)serve the act, nor has any 

 one 3'et recorded either the acts of pollination or oviposition. 

 There will lie nothing peculiar about the latter, but I shall l)e 

 very glad to get actual experience in reference to the former, as 

 I am satisfied that the observed facts will show, still more fully 

 than in the case oi Pronnha yaccasellri, that the special modifica- 

 tions of both flower and insect have gone on until the mutual 

 interdependence has become absolute. 



There is much yet to learn of the pollination of other species 

 of Yucca, and I am particularly anxious to obtain the insects 

 which will doubtless be found associated with them. The reual 



