3. In the present state of our knowledge we have no good ground either to limit the number of specific types beyond what a fair study of our material may warrant, or to infer that such primitive types must necessarily have been of low grade, or that progress in varietal forms has always been upward. The occurrence of such an advanced and specialised type as that of Dadoxylon in the Middle Devonian should guard us against these errors. The creative process may have been applicable to the highest as well as to the lowest forms, and subsequent deviations must have included degradation as well as elevation. I can conceive nothing more unreasonable than the statement sometimes made that it is illogical or even absurd to suppose that highly organised beings could have been produced except by derivation from previously existing organisms. This is begging the whole question at issue, depriving science of a noble department of inquiry on which it has as yet barely entered, and anticipating by unwarranted assertions conclusions which may perhaps suddenly dawn upon us through the inspiration of some great intellect, or may for generations to come baffle the united exertions of all the earnest promoters of natural science. Our present attitude should not be that of dogmatists, but that of patient workers content to labour for a harvest of grand generalisations which may not come till we have passed away, but which, if we are earnest and true to Nature and its Creator, may reward even some of us.
Within the human period great changes of distribution of plants have occurred, chiefly through the agency of man himself, and we have had ample evidence that plants are able to establish themselves and prosper in climates and conditions to which unaided they could not have transported themselves, as, for instance, in the case of European weeds naturalised in Australia and New Zealand. There is, however, no reason to believe that any specific change has occurred to any plant within the Pleistocene or modern period.
In a recent address, delivered to the biological section of the British Association, Mr. Carruthers has discussed this question, and has shown that the earliest vegetable specimens described by Dr. Schweinfurth from the Egyptian tombs present no appearance of change. This fact appears also in the leaves and other organs of plants preserved in the nodules in the Pleistocene clays of the Ottawa, and in specimens of similar age found in various places in Britain and the continent of Europe.[FF]
[FF] “Proceedings British Association,” 1886, “Pleistocene Plants of Canada,” Canadian Naturalist, 1866.
The difficulties attending the ordinary theories of evolution as applied to plants have been well set forth by the same able botanist in his “Presidential Address to the Geological Association in 1877,” a paper which deserves careful study. One of his illustrations is that ancient willow, Salix polaris, referred to in a previous chapter, which now lives in the arctic regions, and is found fossil in the Pleistocene beds at Cromer and at Bovey Tracey.
He notes the fact that the genus Salix is a very variable one, including 19 subgeneric groups and 160 species, with no less than 222 varieties and 70 hybrids. Salix polaris belongs to a subgeneric group containing 29 species, which are arranged in four sections, that to which S. polaris belongs containing six species. Now it is easy to construct a theoretical phylogeny of the derivation of the willows from a supposed ancestral source, but when we take our little S. polaris we find that this one twig of our ancestral tree takes us back without change to the Glacial period. The six species would take us still farther, and the sections, sub-genera, and genus at the same rate would require an incalculable amount of past time. He concludes the inquiry in the following terms:
"But when we have reached the branch representing the generic form we have made but little progress in the phylogenesis of Salix. With Populus this genus forms a small order, Salicineæ, The two genera are closely allied, yet separated by well-marked characters; it is not, however, difficult to conceive of both having sprung from a generalised form. But there is no record of such a form. The two genera appear together among the earliest known dicotyledons, the willows being represented by six and the poplars by nine species. The ordinal form, if it ever existed, must necessarily be much older than the period of the Upper Cretaceous rocks, that is, than the period to which the earliest known dicotyledons belong.
“The Salicineæ are related to five other natural orders, in all of which the apetalous flowers are arranged in catkins. These different though allied orders must be led up by small modifications to a generalised amentiferous type, and thereafter the various groups of apetalous plants by innumerable eliminations of differentiating characters until the primitive form of the apetalous plant is reached. Beyond this the uncurbed imagination will have more active work in bridging over the gap between Angiosperms and Gymnosperms, in finding the intermediate forms that led up to the vascular cryptogams, and on through the cellular plants to the primordial germ. Every step in this phylogenetic tree must be imagined. The earliest dicotyledon takes us not a step farther back in the phylogenetic history of Salix than that supplied by existing vegetation. All beyond the testimony of our living willows is pure imagination, unsupported by a single fact. So that here, also, the evidence is against evolution, and there is none in favour of it.”