SEXUALITY AND THE ENVIRONMENT. 233 



whorls, giving rise to corresponding results of different 

 degrees of development in the respective sexes. 



The points to be clearly perceived are that a plant should 

 be able to develop all its organs in perfection; that there is 

 an optimum degree of energy for each ; and that, though it 

 is customary to group these energies under the two expres- 

 sions, vegetative and reproductive, yet the principle may be 

 carried out in detail : so that, e.g., an enlarged corolla tends 

 to destroy the stamens, as of the ray florets of Dahlia, or even 

 the pistil too, if it be very large, as in Centaurea. A stimu- 

 lated androecium brings about an arrest in the pistil, and 

 causes protandry ; and if the perianth be highly developed, 

 as in orchids, the enhancement of the former may cause 

 degeneracy in the ovules. 



Sexuality axd Nutrition. — Assuming, for the present, that 

 the ancestral condition of all flowers, excepting, perhaps, those 

 of the Gymnosperms, was hermaphrodite, many instances 

 exist of the same species having male, female, and herma- 

 phrodite flowers, such as the Ash, Silene inflata, etc., where 

 the aborted organs often remain more or less rudimentary. 

 It cannot be pretended as yet that the cause or causes can 

 be at all positively asserted, in each case, for the tendency 

 to abortion either in the stamens or pistil ; but there are 

 certain well-ascertained facts which can undoubtedly play a 

 part in the processes of degeneration or exaltation of the 

 stamina! and carpellary energies respectively. If they be 

 sufficiently persistent the subsequent generations can, then, 

 become completely diclinous, without a trace of the other 

 sex remaining ; yet, as is well-known, any diclinous plant 

 may reproduce by reversion the lost sex, thereby revealing 

 its original hermaphroditism. 



In endeavouring to trace the present condition of 

 diclinous flowers back to an ancestral hermaphrodite condi- 



