80 
DARWINISM 
CHAP. 
subsequently shows that, in Xanthoxylum monogynum, ‘ it 
often happens that on the same plant, on the same panicle, 
we find flowers with one or with two ovariesand that this is 
an important character is shown by the Rutacete (to which 
Xanthoxylum belongs), being placed in a group of natural 
orders characterised by having a solitary ovary.” 
“ De Candolle has divided the Crucifer® into five sub-orders 
in accordance with the position of the radicle and cotyledons, 
yet Mons. T. Gay (Ann. clas Scien. Nat., ser. i. tom. vii. p. 389) 
found in sixteen seeds of Petrocalli s Pyrenaica the form of the 
embryo so uncertain that he could not tell whether it ought 
to be placed in the sub orders ‘ Pleurorhizee’ or ‘Notorhizee’; 
so again (p. 400) in Cochlearia saxatilis M. Gay examined 
twenty-nine embryos, and of these sixteen were vigorously 
‘ pleurorhizees,’ nine had characters intermediate between 
pleuro- and notor- hiz^es, and four were pure notorhizees.” 
“M. Raspail asserts (Ann. des Scien. Nat., ser. i. tom. v. p. 
440) that a grass (Nostus Borbonicus) is so eminently variable 
in its floral organisation, that the varieties might serve to 
make a family with sufficiently numerous genera and tribes— 
a remark which shows that important organs must be here 
variable.” 
Species which vary little. 
The preceding statements, as to the great amount of 
variation occurring in animals and plants, do not prove 
that all species vary to the same extent, or even vary at 
all, but, merely, that a considerable number of species in 
every class, order, and family do so vary. It will have 
been observed that the examples of great variability have 
all been taken from common species, or species which have 
a wide range and are abundant in individuals. Now Mr. 
Darwin concludes, from an elaborate examination of the floras 
and faunas of several distinct regions, that common, wide 
ranging species, as a rule, vary most, while those that are 
confined to special districts and are therefore comparatively 
limited in number of individuals vary least. By a similar 
comparison it is shown that species of large genera vary more 
than species of small genera. These facts explain, to some 
extent, why the opinion has been so prevalent that variation 
is very limited in amount and exceptional in character. For 
