10 J. D. Hooker, Introductory Essay to the Flora of Tasmania. 
7. Now the prominent phenomena presented by species under 
cultivation are analogous in kind and extent to those which we 
have derived from a survey of the affinities of plants in a state. 
of nature: a large number remain apparently permanent an 
unalterable, and a large number vary indefinitely. Of the per- 
manent there is little to remark, except that they belong to very 
many orders of plants, nor are they always those which are 
permanent in a state of nature. Many plants, acknowledged by 
1 to be varieties, may be propagated by seed or otherwise, 
te nd we hence find the advocates of 
_ original permanent creations, and those of mutable variable spe- 
cies, taking exactly opposite views in this respect, the truth, I 
believe, being that both are right. Nature has provided for the 
possibility of indefinite variation, but she regulates as to extent 
and duration; she will neither allow her offspring to be weak- 
ened or exhausted by promiscuous hybridization and incessant 
variation, nor will she suffer a new combination of external con- 
ditions to destroy one of these varieties without providing @ 
substitute when necessary; hence some species remain so long 
hereditarily immutable as to give rise to the doctrine that all 
are so normally, while others are so mutable as to induce a be- 
lief in the very opposite doctrine, which demands incessant law- 
less change. 
1 
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