THE SELF-FERTILIZATION OF PLANTS. 375 



are these facts explained, on the view of an occa- 

 sional " dose of medicine " being advantageous or 

 indispensable !" 



Darwin, in striving to explain the causes of the 

 lessened fertility of plants, essays the very ingenious 

 surmise, that " their sexual functions are disturbed." 

 But, it is to be remarked, that he gives not the 

 remotest approach to a conjecture, as to what is the 

 reason for this disturbance ; how it is brought about ; 

 nor why the disturbance is absent in one case, is great 

 in another, is less in a third, and but slight in a fourth. 

 He says, respecting these phenomena (p. 231, Vol. ii, 

 Animals and Plants, &c): 



"We are far from knowing the cause; nor is this 

 surprising, seeing how profoundly ignorant we are in 

 regard to the normal and abnormal action of the 

 reproductive organs." 



It has been shown, with respect to animals, that 

 varieties are generally incapable of long continuing the 

 same form ; that, unless crossing is resorted to, — which 

 varies the form, — or reversion occurs in some of the 

 parts, such varieties die out, and give place to others ; 

 owing to the evil effects resulting from their incom- 

 plete, or disproportionate development. The same 

 holds good, with plants. Varieties, either die out 

 altogether, after a time, or they vary somewhat their 

 form. To this principle, is due the degeneration 

 which, as Darwin has shown, requires that there 

 should be frequent exchanges of seed, or change of 

 conditions. A variety which long remains " genuine," 

 may be relied upon, as being comparatively propor- 



