374 



Fig. 74.— Prodoxus coloeadensis -. «, left 

 front wing, hair-line underneath showing 

 natural size; &, male genitalia, dorsal 

 view — X 15; (■, do., lateral view — X 18. 



however, of how profoundly modified in this particular case the plant 

 and the insect have become in their mutual adaptation, 1 may state 



that tlie perfect Smyrna fig, the most 

 esteemed of tlie edible varieties, can 

 be produced only by the intervention 

 of the Blasfophaga psenes, and that 

 Dr. D. D. Cunningham has recently 

 shown, in the Annals of the Eoyal Bo- 

 tanical Gardens of Calcutta (Vol. i, 

 Appendix I, 1889), by repeated exam- 

 inations of the fruit of Ficus rox- 

 burghii, that pollination, in the ordi- 

 nary meaning of the term, is, in that 

 particular case, out of the question, and that the development of the 

 seed in this species is exclusively due to the stimulation of the tissues 

 caused by the puncturing of the Blas- 

 tophagas; in other words, that these 

 insects actually represent the male ele- 

 ment ill the fertilization. This cer- 

 tainly is the most extraordinary phe- 

 nomenon in the history of fertilization, 

 and if confirmed — and Dr. Cunningham 

 has been most careful and circumspect 

 in his work — it will give a more strik- 

 ing instance than any we have hitherto 

 obtained of the mutual interdependence which plants and insects may 

 attain and the surprising manner in which they may modify each other. 



Fig. 75.— Prodoxus eeticulatus: Female 

 with wings expanded — hair-line showing 

 natural size. 



(tENERALIZATIONS. 



The peculiarities which 1 have endeavored to ]>reseiit to you are full 

 of suggestion, particularly for those who are in the habit of looking 

 beyond the mere facts of observation in endeavors to find .some rational 

 explanation of them ; who, in other words, see in everything they observe 

 significances and harmonies not generally understood. The facts indi- 

 cate clearly, it seems to me, how the peculiar structures of the female 

 Prouuba have been evolved by gradual adaptation to the particular 

 functions which we now find her performing. With the growing adapta- 

 tion to Prouuba's help, the Yucca flower has lost, to a great extent, the 

 activity of its septal glands; yet coincident with this loss we find an 

 increase in the secreting power of the stigma. This increase of the 

 stigmatic fluid doubtless had much to do originally with attracting the 

 moth thereto, \yhile the i)olleniziug instinct doubtless became more 

 and more fixed in proportion as the insect lost the power or desire of 

 feeding. 



With the mind's eye 1 can look back into the past and picture the 

 gradual steps by which the Prodoxids to which I have alluded have 



