Sequoia, a genus of conifers, allied to Taxodium and Cryptomeria, forming one of several surviving links between the firs and the cypresses. The two species are evergreen trees of large size, indigenous to the west coast of North America. Both bear their round or ovoid male catkins at the ends of the slender terminal branchlets; the ovoid cones, either terminal or on short lateral twigs, have thick woody scales dilated at the extremity, with a broad disk depressed in the centre and usually furnished with a short spine; at the base of the scales are from three to seven ovules, which become reversed or partially so by compression, ripening into small angular seed with a narrow wing-like expansion.
The redwood of the Californian woodsmen, S. sempervirens, on which the genus was originally founded by Stephan Endlicher, abounds on the Pacific coast from the southern borders of Oregon southward to about 12 m. south of Punta Gorda, Monterey county, California, forming a narrow mountain forest belt, rarely extending more than 20 or 30 m. from the coast or beyond the influence of ocean fogs, or more than 3000 ft. above sea-level '(see' C. S. Sargent, Silva of North America, vol. x.). It grows to a gigantic size, from 200 to 300 ft. or more in height, with a diameter of from 12 to 15, or rarely 20 to 28 ft. at the much Sequoia sempervirens - a, Branch with green cones and male catkins; b, Section or cone; c, Scale of cone. All slightly reduced.
buttressed base. Professor Sargent refers to it as the tallest American tree, whichprobably occasionally reaches 400 ft. or more in height. In old age the huge columnar trunk rises to a great height bare of boughs, while on the upper part the branches are short and irregular. The bark is red, like that of the Scots fir, deeply furrowed, with the ridges often much curved and twisted. When young the tree is one of the most graceful of the conifers: the stem rises straight and tapering, with somewhat irregular whorls of drooping branches, the lower ones sweeping the ground - giving an elegant conical outline. The twigs are densely clothed with flat spreading linear leaves of a fine glossy green above and glaucous beneath; in the old trees they become shorter and more rigid and partly lose their distichous habit. The cones, from 4 to 1 in. long, are at first of a bluish-green colour, but when mature change to a reddish brown; the scales are very small at the base, dilating into a broad thick head, with a short curved spine below the deep transverse depression. From the great size of the trunk and the even grain of the red cedar-like wood it is a valuable tree to the farmer and carpenter: it splits readily and evenly, and planes and polishes well; cut radially, the medullary plates give the wood a fine satiny lustre; it is strong and durable, but not so elastic as many of the western pines and firs. Professor Sargent describes it as the most valuable timber tree of the forests of Pacific North America. In England the tree grows well in warm situations, but suffers much in severe winters - its graceful form rendering it ornamental in the park or garden, where it sometimes grows 30 or 40 ft. in height; its success as a timber tree would be doubtful. In the eastern parts of the United States it does not flourish. It was discovered by Archibald Menzies in 1795 and was first described as Taxodium sempervirens, under which name it was known until distinguished by Stephan Endlicher as a new genus in 1847.
The only other member of the genus is the giant tree of the Sierra Nevada, S. gigantea, the largest of known conifers; it is confined to the western portion of the great Californian range for a length of about 260 m., at an altitude of from 5000 to 8400 ft. above the sea, and forms extensive forests, or, in the northern part of the area, isolated groves, such as the Calaveras Grove, the Mariposa Grove, and others. The leaves of this species are awl-shaped, short and rigid, with pointed apex; closely adpressed, they completely cover the branchlets. The male catkins are small, solitary, and are borne at the ends of the twigs; the cones are from 12 to 3 in. long, ovoid, with scales thicker at the base than those of the redwood, and bearing below the depression a slender prickle. The young tree is more formal and rigid in growth than S. sempervirens, but when old the outline of the head becomes cylindrical, with short branches sparsely clad with foliage sprays. The bark, of nearly the same tint as that of the redwood, is extremely thick and is channelled towards the base with vertical furrows; at the root the ridges often stand out in buttress-like projections. The average height is about 275 ft. with a diameter near the ground of 20 ft.; but specimens from 300 to 320 ft. tall, with trunks 25-35 ft. thick, are not rare.
The famous group known as the Mammoth Grove of Calaveras in California, containing above ninety large trees, stands in 38° N., about 4370 ft. above the sea, between the San Antonio and Stanislaus rivers. It was discovered by a hunter named Dowd in pursuit of a bear in 1852, but had been visited before by John Bidwill, who crossed the Sierra in 1841. Some trees in the Mariposa Grove rival these in size: one measures for ft. round the root, and a cut stump is 31 ft. in diameter. Gigantic as these trees are and imposing from their vast columnar trunks, they have little beauty, owing to the scanty foliage of the short rounded boughs; some of the trees stand very close together; they are said to be about four hundred in number. The age of the trees has been greatly overestimated. A few years ago a full-sized tree was felled in Fresno county, California, and contiguous transverse sections have been set up, one in the Museum of Natural History at New York, the other (upper one) in the British Museum of Natural History at South Kensington; the annual rings of the latter section have been carefully counted and found to indicate an age of 1335 years.
The growth of the "mammoth tree" is fast when young, but old trees increase with extreme slowness. The timber is not of great value, but the heartwood is dense and of deeper colour than that of S. sempervirens, varying from brownish red to very deep brown; oiled and varnished, it has been used in cabinet work. S. gigantea was brought to England by Lobb in 1853, and received from Dr Lindley the name of Wellingtonia, by which it is still popularly known, though its affinity to the redwood is too marked to admit of generic distinction. In America it is sometimes called Washingtonia. In the Atlantic States it does not succeed; and, though nearly hardy in Great Britain, it is planted only as an ornament of the lawn or paddock.
In early geological times the sequoias occupied a far more important place in the vegetation of the earth. They occur in the Lower Chalk formations, and in Tertiary times were widely diffused; the genus is represented in the Eocene flora of Great Britain, and in the succeeding Miocene period was widely distributed in Europe and western Asia. It is presumed that in the Glacial epoch the genus was exterminated except in the areas in western North America where it still persists.
