68 SPECIES OF LAEGEE GENEEA VAEIABLE. [Chap. II. 



species, tlie 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 live 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 more 

 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 all those in the smaller 

 genera on the other side, the former will be found to 

 include a somewhat larger number of the very common 

 and much diffused or dominant species. This might 

 have been anticipated ; for the mere fact of many 

 species of the same genus inhabiting any country, 

 shows that there is something in the organic or 

 inorganic conditions of that country favourable to the 

 genus ; and, consequently, we might have expected to 

 have found in the larger genera, or those including 

 many species, a larger proportional number of dominant 

 species. But so many causes tend to obscure this 

 result, that I am surprised that my tables show even a 



