THE YUCCA MOTH AND YUCCA POLLINATION. 171 

 THE YUCCA MOTH AND YUCCA POLLINATION.* 



By C. V. RILEY, Ph. D. 



THE common belief, based upon the theological assumption 

 that all things upon this terrestrial sphere are for man's espe- 

 cial benefit, was, and perhaps yet is, that flowers were endowed 

 with beauty and fragrance for our particular pleasure. Let us 

 look somewhat more closely into this matter, and see what mod- 

 ern science has to say about it. Ever since Linnseus used the 

 sexual characteristics of flowers in classification, and Erasmus 

 Darwin sang of the loves of the plants, the philosophy of fertili- 

 zation in the plant kingdom has been fairly apprehended. It has 

 long been recognized that plants are divisible into homomorphic 

 or self-fertilizable, and heteromorphic or cross-fertilizable species. 

 All diclinous plants, or those having separate male and female 

 flowers, belong to the latter category, which is further classifiable 

 according to the means by which cross-fertilization is effected. 

 One class (termed anemojiliilcz) depend almost entirely on the 

 wind, and in these, of which our pines and other conifers, our 

 poplars, willows, grasses, etc., are examples, the pollen or male 

 element obtains in enormous quantities, is easily detached, and is 

 generally produced early in spring, when winds prevail, and fre- 

 quently before the development of the leaves, which would tend 

 to impede its dispersion. The flower is inconspicuous and the 

 stigma or female organ generally branched or hairy, so as to in- 

 crease the chance of catching the wind-borne pollen. "Water is an 

 agency in the fertilization of a few plants, of which the singular 

 Vallisneria is a striking illustration ; while a few are aided by 

 birds and higher animals; but by far the greater number are fer- 

 tilized, or, more strictly speaking, pollinized, by insects. 



The most casual observer of Nature must have appreciated, 

 years ago, the fact that flowers are very important to insects, fur- 

 nishing the essentials of life to those of several orders, and espe- 

 cially to the Hymenoptera (bees, wasps, etc.) and Lepidoptera 

 (butterflies and moths) in the form either of pollen or nectar. 

 But that insects could be of any especial benefit to plants has 

 only come to be acknowledged and fully appreciated of late years. 

 Toward the close of the last century Christian Konrad Sprengel 

 published an important work Das entdeckte Geheimniss der 

 Natur in which he maintained that the color, form, odor, secre- 

 tions, and the general structure of flowers had reference to insects 

 which are essential as pollinizers. The importance of insects as 



* Adapted from advance sheets of the Annual Report of the Missouri Botanical Garden 

 for 1891. 



