DARWIN ON PRIMULA. 243 



facts to work upon. It must suffice to suggest coujecturally that 

 a conservative agency, if we may so term it, is at work in the 

 vegetable kingdom, over and above the inherent check of a hke 

 tendency possessed in a high degree by the great majority of species, 

 which absolutely prevents miscellaneous or Avide hybridization or 

 crossing. We do not forget that the question of hybridization of 

 distinct species may be entered upon, to a certain extent, apart from 

 that of the crossing of different individuals of the same species, and 

 that a most important distinction may be drawn between them, but 

 facts fail to show how far the check which prevents a crossing of 

 species operates in preventing too wide a crossing of individuals of 

 any one species, if indeed it operate in the latter case at all. "We 

 have alluded to what have seemed to be special contrivances in 

 certain flowers to prevent self-fertilization. Several familiar cases 

 might be quoted but we have already exceeded a reasonable limit, 

 and until some more careful observers, with a measure of that 

 earnest diligence in an unprejudiced search after truth, which so 

 pre-eminently characterizes Mr. Darwin, shall have described to iis 

 the true character and end of some of these anomalous structures it 

 would be useless to offer any blind speculations with regard to them. 

 Einally, let us beg those who have opportunity, — and but a short 

 time each day, if perseveringly devoted to the purpose, Avill suffice 

 for important results, — let us beg that they will select for careful 

 watching and study either one of the common cases of dimorphism 

 mentioned above, or some of the plants which we have adverted to 

 as offering obstacles to self-fertilization. Either class promises well 

 to be resultful. Let us just observe that it is by no means essential 

 that the observer should be a " botanist." Mr. Darwin is not a 

 botanist, nor did he ever pretend to be such, yet his observations 

 prove of the very highest value to botanical science. 



[In the above paper we have not referred to the phenomenon of 

 dimorphism exhibited by various Orchidaceae. AYe hope to return 

 to the subject, in connection with Mr. Darwin's new work on the 

 ' Fertilisation of Orchidaceae ' in a future number.] 



