Vlli FLORA OP 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 and unalterable, and a large number vary 
indefinitely. Of the permanent 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 all to be varieties, may be propagated by seed or otherwise, when their offspring re- 
tains for many successive generations the characters of the variety. On the other hand, species 
which have remained immutable for many generations under cultivation, do at length < 
vary, and having once begun, are thereafter peculiarly prone to vary further. 
8. The variable cultivated species present us with the most important phei 
gating the laws of mutability and permanence ; but these phenomena are so infinitely varied, com- 
plex, and apparently contradictory, as to defeat all attempts to elucidate the history of any individual 
case of variation by a study of its phases alone. It would often appear doubtful whether the natural 
operations of a plant tend most to induce or to oppose variation ; and we hence find the advocates of 
original permanent creations, and those of mutable variable species, 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 it as to extent and duration ; she will neither allow her offspring 
to be weakened or exhausted by promiscuous hybridization and incessant variation, nor will she suffer 
a new combination of external conditions to destroy one of these varieties without providing a sub- 
stitute when necessary j 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 belief- in the very 
opposite doctrine, which demands incessant lawless change. 
9. It would take far too long a time were I to attempt any analysis of the phenomena of culti- 
vation, as illustrative of those of variability in a state of nature. There are however some broad facts 
which should be borne in mind in treating of variation by cross impregnation and hybridity. 
10. Variation is effected by graduated changes ; and the tendency of varieties, both in nature 
and under cultivation, when further varying, is rather to depart more and more widely from the 
original type, than to revert to it : the best marked varieties of a wild species occurring on the 
confines of the area the species inhabits, and the best marked varieties of the cultivated species 
being those last produced by the gardener. I am aware that the prevalent opinion is that there is a 
strong tendency in cultivated, and indeed in all varieties, to revert to the type from which they de- 
parted ; and I have myself quoted this opinion, without questioning its accuracy,' 55 ' as tending to sup- 
subject to the influence of fundamentally different laws. He says, "No inferences as to varieties in a state of 
nature can he deduced from the observation of those occurring among domestic animals. The two are so much op- 
posed that what applies to the one is almost sure not to apply to the other." But, in the first place, of the same species 
of wild animals some families must be placed where certain faculties and senses are far more exercised than others, 
and the difference in this respect between the conditions of many families of wild animals is as great as those between 
many wild and tame families ; and secondly, other senses and faculties, latent and unknown in the wild animal, but 
which are as proper to the species as any it exercised in its wild state, are manifested or developed by it under 
domestication. An animal in a state of nature is not then, as Mr. Wallace assumes, " in the full exercise of every 
part of its organization ;" were it so, it could not vary or alter with altered conditions, nor could other faculties re- 
main to be called into play under domestication. The tendency of species when varying cannot be to depart from 
the original type in a wild condition and to revert to it under domestication, for man cannot invert the order of 
Nature, though he may hasten or retard some of its processes. 
* FL N. Zeal., Introd. Essay, p. x., and Flora Indica, Introduction, p. 14. 
