Chap. II. DOMINANT SPECIES VARY MOST. 53 



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. 

 C. 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 subse- 

 quently Dr. Hooker, even in stronger terms. I shall 

 reserve for my future work the discussion of these dif- 

 ficulties, and the tables themselves of the proportional 

 numbers of the varying species. Dr. Hooker permits 

 me to add, that after having carefully read my manu- 

 script, and examined the tables, he thinks that the fol- 

 lowing 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 dis- 

 cussed. 



Alph. De Candolle and others have shown that plants 

 which have very wide ranges generally present varieties ; 

 and this might have been expected, as they become ex- 

 posed to diverse physical conditions, and as they come 

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

 far more important circumstance) with different sets of 

 organic beings. But my tables further show that, in 

 any limited country, the species which are most common, 

 that is abound most in individuals, and the sjDecies which 

 are most widely diffused within their own country (and 

 this is a different consideration from wide range, and to 

 a certain extent from commonness), often give rise to 

 varieties sufficiently well-marked to have been recorded 

 in botanical works. Hence it is the most flourishing, 

 or, as they may be called, the dominant species, — 



