XXIV FLORA OF TASMANIA. 
of the Genera and Orders most deficient in these respects are so manifestly reduced members of 
others, which are indisputably the most complex in organization in the whole Vegetable Kingdom, 
that no good classification even has been founded on these considerations alone.* 
37. Again, it is argued by both Mr. Darwin and Mr. Wallace that the general effects of variation 
by selection must be to establish a general progressive development of the whole animal kingdom. 
But here again in botany we are checked by the question, What is the standard of progression ? 
Is it physiological or morphological ? Is it evidenced by the power of overcoming physical obstacles 
to dispersion or propagation, or by a nice adaptation of structure or constitution to very restricted or 
complex conditions? Are cosmopolites to be regarded as superior to plants of restricted range, her- 
maphrodite plants to unisexual, parasites to self-sustainers, albuminous-seeded to exalbuminous, gym- 
nosperms to angiosperms, water plants to land, trees to herbs, perennials to annuals, insular plants 
to continental ? and, in fine, what is the significance of the multitudinous differences in point of 
structure and complexity, and powers of endurance, presented by the members of the Vegetable 
Kingdom, and which have no recognized physiological end and interpretation, nor importance in a 
classificatory point of view? It is extremely easy to answer any of these questions, and to support 
the opinion by a host of arguments, morphological, physiological, and teleological ; but any one gifted 
with a quick perception of relations, and whose mind is stored with a sufficiency of facts, will turn 
every argument to equal advantage for both sides of the question. 
To my mind, however, the doctrine of progression, if considered in connection with the hypothesis 
of the origin of species being by variation, is by far the most profound of all that have ever agitated 
the schools of Natural History, and I do not think that it has yet been treated in the unprejudiced 
spirit it demands. The elements for its study are the vastest and most complicated which the 
naturalist can contemplate, and reside in the comprehension of the reciprocal action of the so-called 
inorganic on the organic world. Granting that multiplication and specialization of organs is the 
evidence and measure of progression, that variation explains the rationale of the operation which 
results in this progression, the question arises, What are the limits to the combinations of physical 
causes which determine this progression, and how can the specializing power of Nature stop short of 
causing every race or family ultimately to represent a species? While the psychological philosophers 
persuade us that we see the tendency to specialize pervading every attribute of organic life, mental 
and physical; and the physicists teach that there are limits to the amount and duration of heat 
light, and every other manifestation of physical force which our senses present or our intellects per- 
ceive, and which are all in process of consumption ; the reflecting botanist, knowing that his ultimate 
results must accord with these facts, is perplexed at feeling that he has failed to establish on inde- 
pendent evidence the doctrines of variation and progressive specialization, or to co-ordinate his 
attempts to do so with the successive discoveries in physical science. 
• The subject of the retrogression of types lias never yet been investigated in botany, nor its importance esti- 
umumes of this nature. To whatever Order we may grant the dignity of great superiority or coi 
tat Order containing groups of species of very simple organization ; these are moreover often of great size 
and importance, and of wide geographical distribution. Such groups, if regarded per se, appear to be far lower in 
on than other groups which are many degrees below them in the classified a ri< 3 ; ,-,,.1 on, only clue to 
oZrlr*7: f heii ; e T ent f nity ^ their compiex »-*"•-*-*•** «- ^ by . j*^ 
« 1 7vtZ I t ■ P ° Sltl0n ° f ^ f0rmCT ^ bC l0St - Are SUCk «™P» of ^Ply-constructed 
nria^l^^^ 8 ^ Vamtl ° n ° f ^ ^^ ° r dld the ^ P roceed f ^- them by progressive variation P 
in the Ld , T P nnS Pr6Cede * ° rigin thC hi " beSt f0ms of al1 other S™P ^ich rank below them 
