336 Notice of Dr. Hooker’s Flora of New Zealand. 
tions presented by many plants of indubitably one and the same 
species, and the still wider diversities of long cultivated races 
from an original stock, they would find more than one instructive 
parallel to the case of the longest-domesticated of all species, man. 
Let it also be especially noted, that varieties are not always, 
not even generally, the result of external agencies, at least of 
‘such as we are able to detect. Certain varieties of plants are so 
originated: these are generally as transient as the cause that pro- 
duces them, and under altered circumstances often disappear even, 
during the life of the individual: the plant may outgrow them. 
of a polymorphous plant such as a Coprosma, Metrosideros or 
Alseuosmia in New Zealand, and any difference of circumstances 
attributable to station ; still more so when these diversities occur 
side by side. Yet such are the varieties which ordinarily exhibit 
the greatest persistency, i.e. when kept from intermingling by 
mutual fecundation ha n 
least account for the origin of the race of «Dorking fowls, or 
Manx eats, or indeed of almost any of our domesticated races 
which were not produced by cross-breeding, that is by mingling 
the characters of two such races already in existence. Yet how 
brief, but very decided and remarkable. He has already declare 
in the previous section ‘that it is by far the smaller half of t 
vegetable kingdom that is confined to narrow geographical of 
climatic areas, and that very few plants indeed are absolutely 
local ; whilst the operations of the gardener and agriculturist prove 
a vast proportion of the plants of the two temperate geen 
to the distribution and variation of species, can have consid si 
a garden in a philosophical spirit, or have weighed such facts 
