246 THE STRUCTURE OF FLOWERS. 



Mr. Darwin showed that seeds of the female plants of Thyme 

 yielded both female and hermaphrodite plants. 



Although, therefore, we are unable to fathom all the 

 mysteries of Nature's procedure, we can detect some of the 

 lines upon which she works, and perceive how, in all cases, 

 it is the environment — but sometimes one set of influences, 

 sometimes another — which, being brought to bear upon the 

 plant, the latter responds to it; and some form of what 

 may be called "incipient diclinism " is the first result. If, 

 then, these influences be kept up, hereditary conservatism 

 comes into play, and such slight beginnings towards a 

 separation of the sexes becomes fixed — only temporarily, 

 however, — which constitute the first step, to be followed by 

 others, till absolute and almost irrevocable dioecism is the 

 final result. 



Dr. M. T. Masters has collected several cases in which 

 one or other of the sexes has been ari-ested, apparently in 

 consequence of the nature of the soil and other conditions of 

 the environment. I i-efer the reader to his " Teratology," as 

 my object is not merely to enumerate all the instances known, 

 but sufficient to establish the theory advanced, — that it is the 

 environment that first influences the organism, which then 

 responds to it ; and that, secondly, all adaptive variations 

 thus set up — provided the environment continue to exert its 

 influences — can become fixed by heredity. The consequence 

 is that they are ultimately recognized as constant and 

 specific characters. 



The Origin of Sex. — If now the environment has been 

 proved to exert potent effects upon the development of the 

 sexual apparatus of flowers, there still remains the ques- 

 tion how far is either sex or both present, or at least poten- 

 tial, in the embryo. Marked differences have resulted from 

 sowing fresh or well-matured and older seeds of melons. 



