54 
DOMINANT SPECIES YAKY MOST. 
Chap.TI. 
those wliicli range widely over the world, are the most 
diffused in their own country, and are the most numerous 
in individuals,—which oftenest produce well-marked 
varieties, or, as I consider them, incipient species. And 
this, perhaps, might have been anticipated; for, as 
varieties, in order to become in any degree permanent, 
necessarily have to struggle with the other inhabitants 
of the country, the species which are already dominant 
will be the most likely to yield offspring, which, though 
in some slight degree modified, still inherit those advan¬ 
tages that enabled their parents to become dominant 
over their compatriots. 
If the plants inhabiting a country and described in 
any Flora be divided into two equal masses, all those in 
the larger genera being placed on one side, and all those 
in the smaller genera on the other side, a somewhat 
larger number of the very common and much diffused or 
dominant species will be found on the side of the larger 
genera. This, again, might have been anticipated; for 
the mere fact of many species of the same genus in¬ 
habiting 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 large proportional num¬ 
ber of dominant species. But so many causes tend to 
obscure this result, that I am surprised that my tables 
show even a small majority on the side of the larger 
genera. I will here allude to only two causes of 
obscurity. Fresh-water and salt-loving plants have 
generally very wide ranges and are much diffused, 
but this seems to be connected with the nature of the 
stations inhabited by them, and has little or no relation 
to the size of the genera to which the species belong. 
Again, plants low in the scale of organisation are 
