136 Trans. Acad. Sci. of St. Louis. 



in these organs exists for the sole purpose of attracting to 

 them insects, sometimes of one, sometimes of another kind 

 (for which it is protected from rain and dew and commonly 

 from other classes of insects, and to which its presence is 

 made known by odor and color, and its position by grooves 

 and other guiding mechanism and by variegation in the col- 

 oring), which, while serving their own purposes, ensure the 

 pollination of some flowers which might attain the same end 

 directly as well of others which from some seeming freak of 

 nature mature stamens and pistils at different times or even 

 have them separated in different flowers, — sometimes, even, 

 on different individuals. A half century later, Mr. Darwin, 

 seeing in floral forms, colors and odors something more than 

 means of overcoming chance defects in plan or development, 

 showed not only the general accuracy of Sprengel's conclu- 

 sions as illustrated by a host of other cases, but that they 

 might be carried a step further, by stating the purpose of the 

 structural and functional peculiarities in question to be the 

 effecting of cross fertilization. Then he set to work to prove, 

 by a long-continued series of experiments, whether or not 

 this is connected with a gain to the offspring resulting from 

 such crosses, and we cannot question the resulting conclusion 

 that it is. Indeed it may be asked if any axiom is more im- 

 portant to an understanding of the evolutionary adaptation of 

 species to changing environment than the obvious conclusion 

 that sex, and particularly the partition of the sexes with sec- 

 ondary provisions of the most varied kinds for their functional 

 union, is a most potent factor for the introduction of variation 

 within helpful limits, on which natural selection may build 

 with the current of the times, as well as for the direct bet- 

 terment of the offspring. 



How dissemination is effected, and the structures connected 

 with it ; how plants may climb to the light and air with a 

 minimum expenditure of material, over their more robust 

 competitors when the latter have reached their own limit in 

 the occupation of the soil ; how they may feed upon each 

 other and upon animals ; how they may extend into deserts 

 and the salt sea : — these and many other questions show the 

 range of ecology as it is now occupying alike physiologists^ 



