50 I)OMIjS'ANT SPECIES VARY M0S7\ 



with plants by Gaston de Saporta. If a variety were to 

 flourish so as to exceed in numbers the parent species, it 

 would then rank as the species, and the species as the 

 variety; or it might come to supplant and exterminate the 

 parent species; or both might co-exist, and both rank as 

 independent species. But we shall hereafter return to this 

 subject. 



From these remarks it will be seen that I look at the 

 term species as one arbitrarily given, for the sake of con- 

 venience, to a set of individuals closely resembling each 

 other, and that it does not essentially differ from the term 

 variety, which is given to less distinct and more fluctuating 

 forms. The term variety, again, in comparison with mere 

 individual differences, is also ajoplied arbitrarily, for con- 

 venience sake. 



WIDE-KANGII^G, MUCH DIFFUSED, AND COMMO]!f SPECIES 



VARY MOST. 



Guided by theoretical considerations, I thought that 

 some interesting results might be obtained in regard to the 

 nature and relations of the species which vary most, by 

 tabulating all the varieties in several well- worked floras. 

 At first this seemed a simple task; but Mr. H. 0. Watson, 

 to whom I am much indebted for valuable advice and 

 assistance on this subject, soon convinced me that there 

 were many difficulties, as did subsequently Dr. Hooker, 

 even in stronger terms. I shall reserve for a future work 

 the discussion of these difficulties, and the tables of the 

 proportional numbers of the varying species. Dr. Hooker 

 permits me to add that after having carefully read my 

 manuscript, and examined the tables, he thinks that the 

 following statements are fairly well established. The whole 

 subject, however, treated as it necessarily here is with much 

 brevity, is rather perplexing, and allusions cannot be 

 avoided to the *^ struggle for existence," '^divergence of 

 character," and other questions, hereafter to be discussed. 



Alphonso de Candolle and others have shown that 

 plants which have very wide ranges generally present 

 varieties; and this might have been expected, as they are 

 exposed to diverse physical conditions, and as they come 

 into competition (which, as we shall hereafter see, is an 

 equally or more important circumstance) with different 



