Fig. 15. Sequoia Couttsiae Heer. Twigs (A) and cone-scales (B) from Bovey Tracey. (× 3.) (Photographs by Mr and Mrs Clement Reid.)
It is, however, in the sedimentary rocks of Cretaceous age, rather higher in the series than those in the Hastings cliffs, and in the succeeding Tertiary rocks, that undoubted Sequoias are met with in abundance. At Bovey Tracey in Devonshire there is a basin-shaped depression in the granitic rocks of Dartmoor filled with clay, gravel and sand—the flood-deposits of a Tertiary lake containing waifs and strays of the vegetation on the surrounding hills. Among the commonest plants is one to which the late Oswald Heer gave the name Sequoia Couttsiae, and his reference of the specimens to the genus Sequoia has been confirmed by the recent researches of Air and Mrs Clement Reid([50]). This Tertiary (Oligocene) species is represented by slender twigs almost identical with those of Sequoia gigantea and by well-preserved cone-scales and seeds ([Fig. 15]). Moreover, it has been possible to examine microscopically the structure of the carbonised outer skin of the leaves and to demonstrate its agreement with that of the superficial tissue in the leaves of the Mammoth tree. With the Bovey Tracey Sequoia are associated fragments of Magnolia, Vitis, and Taxodium distichum, the swamp Cypress of North America, together with other types which have long ceased to exist in Western Europe. Other British examples of Sequoia have been described from Tertiary beds at Bournemouth, the Isle of Wight, Sheppey, and Antrim, but the material from these localities is inferior in preservation and cannot be identified with the same degree of certainty as in the case of the Devonshire specimens. The occurrence of twigs and cones of several species of Sequoia in both Cretaceous and Tertiary rocks in Austria, Germany, Italy, France, and elsewhere, shows that the ancestors of the Californian trees were common in the European region.
The exploration of Cretaceous and Tertiary rocks in Arctic Europe has revealed the former existence in Greenland, Spitzbergen, and other more or less ice-covered lands of plants which clearly denote a mild climate. Cones and branches of Sequoias have been found in abundance in Lower Tertiary beds on Disco Island off the west coast of Greenland, and similar evidence of the northern extension of the genus has been obtained from Spitzbergen. Dr Nathorst of Stockholm speaks of twigs of Sequoia in the Tertiary clays of Ellesmere Land almost as perfect as herbarium specimens. In Tertiary beds on the banks of the Mackenzie River, in Alaska, Saghalien Island and Vancouver Island, and in Upper Cretaceous rocks in the Queen Charlotte Islands, remains of Sequoia have been discovered. One of the most remarkable instances of the preservation of trees of a bygone age is supplied by the volcanic deposits of Lower Tertiary age exposed on the slopes of Amethyst mountain in the Yellowstone Park district. At different levels in the volcanic and sedimentary material, which is piled up to a height of over 2000 ft. above the valley, as many as fifteen forests are represented by erect and prostrate limbs of petrified trees ([Fig. 6]). The microscopical examination of some of these trees has shown that they bear a striking resemblance to Sequoia sempervirens. In a photograph of these petrified forests by the U.S. Geological Survey (36, 2) one sees living Conifers side by side with the lichen-covered and weathered trunks of the fossil species (Sequoia magnifica), living and extinct being at a distance hardly distinguishable. (Frontispiece.)
In concluding this brief survey of the fossil records of Sequoia, reference may be made to the discovery of petrified wood in Cretaceous rocks in South Nevada, possessing the anatomical features of Sequoia gigantea, which shows that close to the present home of the big trees their ancestors flourished during a period of the earth's history too remote to be measured by human reckoning.
The distribution of the Tertiary and Cretaceous Sequoias would appear to have been mainly in the northern hemisphere, extending well within the Arctic circle. It is, however, by no means improbable that the ancestors of Sequoia flourished far south of the equator. Reference has been made to Jurassic fossils from Madagascar which have been compared with the existing species, and from Lower Tertiary beds in New Zealand the late Baron Ettingshausen described some cones and twigs as Sequoia novae zeelandicae which bear a close resemblance to the existing type. The available evidence would seem to point to a northern origin of the genus, though allowance must be made for erroneous conclusions based on negative evidence. Further research may well extend the past distribution of Sequoia in southern lands, but the data to hand point to the conclusion that the Californian trees represent the survivors of a type which flourished in the Cretaceous and Tertiary periods over a wide area in North America and in what we now call the Continent of Europe.
[CHAPTER VII]
THE ARAUCARIA FAMILY
'And so the grandeur of the Forest-tree
Comes not by casting in a formal mould,
But from its own divine vitality.'