[CHAPTER IV]
PRESERVATION OF PLANTS AS FOSSILS
'Some whim of Nature locked them fast in stone for us afterthoughts of Creation.' Lowell.
The failure of the earlier naturalists to grasp the true significance of fossils or even to appreciate their nature is an extraordinary fact when we consider the pioneer work which they accomplished in biological and geological science. The following extract from the writings of so enlightened a man as John Ray serves to illustrate an almost incredible disinclination to admit what seems to us the obvious. He wrote:—'Yet I must not dissemble that there is a Phenomenon in Nature, which doth somewhat puzzle us to reconcile with the prudence observable in all its work, and seems strongly to prove, that Nature doth sometimes ludere, and delineates figures, for no other end, but for the ornament of some stone, and to entertain or gratify our curiosity, and exercise our wits. This is, those elegant impressions of leaves and plants upon cole-slate, the knowledge of which, I must confess myself to leave to my learned and ingenious friend Mr Edward Lhwyd of Oxford.... He told me that Mr Woodward, a Londoner, shewed him very good draughts of the common female fern, naturally formed in cole.... But these figures are more diligently to be observed and considered... Dr Woodward will have them to be the impressions of the leaves of plants which were there lodged at the time of the Deluge'([31]).
The Mr Woodward alluded to by Ray thus expressed his views on fossils in an Essay towards the Natural History of the Earth:—'The whole terrestrial globe was taken all to pieces and dissolved at the Deluge, the particles of stone, marble, and all solid fossils dissevered, taken up into the water, and then sustained together with sea shells and other animal and vegetable bodies; the present earth consists and was formed out of that promiscuous mass of sand, earth, shells, and the rest falling down again, and subsiding from the water'([32]).
In the later part of the seventeenth-century Steno, a Dane by birth and Professor of Anatomy at Padua, by his recognition of the identity of the teeth in a shark's head, which he had dissected, with some fossils from Malta known as Glossopetrae, established the true nature of fossils. He also recognised a certain orderly sequence in fossiliferous strata, and in the opinion of Professor Sollas he is entitled to be considered the 'Father and Founder' of Geology([33]).
It was by slow degrees that the early observers freed themselves from the obsession that the remains of animals and plants in the earth's crust bear witness to a Universal Deluge and are all identical with existing species. The possibility that some of the fossil plants in English strata might be more clearly related to forms now met with in warmer regions was gradually realised. The publication of the Origin of Species stimulated palaeontological research, and botanists as well as zoologists turned to the investigation of extinct genera in search of proofs of the doctrine of evolution.
The common occurrence of petrified wood in rocks of different ages is well known. Fossil stems are occasionally found in their natural position of growth, the structural details being rendered permanent by the deposition of siliceous or calcareous material from water drawn by capillarity into the dead but still sound tissues. Petrified wood from Upper Jurassic beds is abundant in the Island of Purbeck; an unusually long piece of stem may be seen in the small town of Portland fixed to the wall of a house. Some of these stems have been referred by an American author to the Araucarian family of Conifers, but the structure is as a rule hardly well enough preserved to afford satisfactory evidence for identification. In his Testimony of the Rocks, Hugh Miller speaks of fossil wood from the upper beds of the Jurassic system in sufficient abundance on the beach at Helmsdale in Sutherlandshire to be collected in cart-loads; it is still easy to pick up good specimens on the shingle beach a short distance north of Helmsdale, and a recent microscopical examination showed that some specimens are pieces of an Araucarian tree.