40 SPECIES OF LARGER GENERA VARIABLE. [CHAP. II. j 



allusions cannot be avoided to the " struggle for existence," 

 "divergence of character," and other questions, hereafter to be 

 discussed. 



Alphonse 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 sets of organic beings. But my tables further show that, ; 

 in any limited country, the species which are the most common, 

 that is abound most in individuals, and the species which are most I 

 widely diffused within their own country (and this is a different ) 

 consideration from wide range, and to a certain extent from j' 

 commonness), oftenest 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, those which range widely, are the most diffused in their | 

 own country, and are the most numerous in individuals, which I 

 oftenest produce well-marked varieties, or, as I consider them, | 

 incipient species. And this, perhaps, might have been anticipated ; a 

 for, as varieties, in order to become in any degree permanent, I 

 necessarily have to struggle with the other inhabitants of the I 

 country, the species which are already dominant will be the most I 

 likely to yield offspring, which, though in some slight degree I 

 modified, still inherit those advantages that enabled their parents f' 

 to become dominant over their compatriots. In these remarks 

 on predominance, it should be understood that reference is made 

 only to the forms which come into competition with each other, 

 and more especially to the members of the same genus or class 

 having nearly similar habits of life. With respect to the number 

 of individuals or commonness of species, the comparison of course 

 relates only to the members of the same group. One of the 

 higher plants may be said to be dominant if it be more numerous 

 in individuals and more widely diffused than the other plants of 

 the same country, which lire under nearly the same conditions. 

 A plant of this kind is not the less dominant because some 

 conferva inhabiting the water or some parasitic fungus is infinitely 

 more numerous in individuals, and more widely diffused. But if 

 the conferva or parasitic fungus exceeds its allies in the above 

 respects, it will then be dominant within its own class. 



Species of the Larger Genera in each Country vary move frequently 

 than the Species of the Smaller Genera. 



If the plants inhabiting a country, as described in any Flora, 

 be divided into two equal masses, all those in the larger genera 

 (i.e., those including many species) being placed on one side, and 



