FOSSIL CONIFER Æ.

170. We have already described this family (77) and illustrated its structure (Ling. 4 and 5); but as remains of cone-bearing trees are found in geological strata in nearly every part of the world, and often in such quantities and of such sizes as to excite peculiar attention, the subject seems to claim some additional notice.

Most of the wood of this genus found in the British mines appears to have been of the species araucaria, (80,) of which the celebrated Norfolk pine, one of the largest trees now growing, is a member. But one of the most extraordinary and interesting assemblages of these trees is that in the Isle of Portland, England, where an entire forest of pines appears to have been transformed into stone on the very spot on which it grew; the Cycadeæ still shooting up, as it were, between the trunks and roots of the trees, though changed into flint, extending into the bed of mold from which they originally derived their support.

In the sands of the desert of Sahara in Egypt; among the bones of the mammalia near the Himalaya mountains, and in the tertiary deposits of Virginia, drifted coniferous wood, associated with Cycadeæ, have been discovered. Trees of this family, of a highly interesting character, are also found in various parts of Australia and Van Dieman's Land. In the latter country these trees of stone are described as standing erect to the height of several feet, in a bed of arid sand, apparently in the places where they grew; their petrified stems and branches being scattered around them. So entirely do these trees of stone preserve their natural woody appearance, that one of the emigrants relates, among the extraordinary sights he witnessed in New Holland, the burning of trees to manure the ground.

A still more extraordinary forest of petrified stumps is described by Rev. Mr. Clark, as existing in Australia. Stumps of fossilized trees are seen projecting out of the ground, presenting the appearance of a forest in which the trees are all cut down to the same level. At the distance of some yards from the shore, a reef is formed by vertical rows of the petrified stems, which project above the surface

What is said of the distribution of fossil pines? What is said of the petrified forest of Australia? How is this accounted for?

of the water. Those on the land stand generally about three or four feet above the surface, and are from two to six feet in diameter. The wood is silicified, and veins of chalcedony traverse the substance of the trunks between the concentric rings and medullary rays. In several examples, from sixty to one hundred and twenty annual rings were observable. As to any hypothesis of the means by which this forest was petrified, no remarks are offered; but it is certain, that these trees must have been in a different situation, when this was effected; for the atmosphere, or the waters of the ocean, never produce such changes. They must therefore have, at some period, been under the earth, perhaps by the subsidence of the ground on which they stood, and after being petrified, raised by volcanic force to their present situation.

FOSSIL PALMS.

171. This family at the present day are exclusively natives of intertropical climates, and are remarkable for their elegant forms and striking aspects. The Date, Cocoa-nut, Talipot, Fan-palm and many others, are members of this large and magnificent genus. They have a single cylindrical stem, sometimes growing to the height of a large ship's mast, with a top spreading out like a canopy, and sometimes consisting of leaves twenty feet long, and nearly as many wide. The trunks and even leaves of this family are found in the fossil state in various parts of the world. Dr. Buckland states, that stems of palms, beautifully silicified, occur in the tertiary deposits of Hungary. They are also found in France, Italy and the West Indies. In England they occur in the oolite formations and in coal fields. Nor is the United States without her share of these tropical relics, a group of fossil palm-trees having been discovered and described by Dr. Owen, of New Harmony, in the state of Indiana. It occurs in one of the upper members of the Illinois coal-fields, where from twenty to thirty trees were found, with their main roots attached and ramifying in the clay, and their stems in the coal and sandstone above, as if submerged on the spot where they originally grew. A carbonaceous

What is said of the recent palms? What is said of the distribution of fossil palms? What locality is mentioned in this country?

crust envelopes the trunks, which are covered with lozenge-shaped scars, having a transverse direction, and presenting a diversity of figures in the attachment of the petioles, which indicates at least three species of this genus. Silliman's Journal, 1843.

Change of Climate.-"It is not surprising," says Dr. Buckland, "to find the remains of palms in warm latitudes, where this family are now indigenous, as in Antigua and India; but their occurrence in the tertiary formations of Europe, (and we may say of North America also,) associated with the remains of crocodiles and tortoises, and with marine shells, nearly allied to forms which are at present found only in seas of a warm temperature, seems to indicate that the climate of Europe, during the tertiary period, was warmer than it is at present."

FOSSIL LEAVES.

172. Palm-leaves occur in France, Switzerland and Tyrol, but differ materially from any living species. These leaves are said to be too well preserved to have endured transportation by water from a distant region, and must therefore be referred to extinct species, which in the tertiary period were indigenous in Europe.

Foliage of Dicotyledonous plants.-These are of frequent occurrence in the tertiary marls and limestones of England, and are sometimes abundant, and in good preservation. But more perfect examples occur in the tertiary strata near Pavia in Italy. These leaves belong to several genera of ligneous dicotyledons, and most of them to species which still grow in the vicinity. In some cases the substance of the leaf is changed into carbon, the structure being well preserved; but, in general, sharp and well-defined imprints only are left on the stone, being exact copies of the outlines and larger veins of the originals. They are found in a gypseous marl, of a cream color; and from their perfect state, it is inferred that they were enveloped in the soft matrix, where they are found, soon after their fall, and were preserved by the rapid hardening of the strata. Lign. 26. It will be obvious from the figures that all these leaves are of species now growing. No. 1, Poplar, Populus græca. 2, Maple, Acer. 3,

What indications with respect to climate are inferred from this fact?

Water-spike, Potamogeton. 4, Willow, Salix. 5, Chestnut, Esculus. From what has been remarked heretofore, it is an exceedingly rare occurrence to detect fossil remains, either of animals or plants, of the species now living, though genera of the ancient and present Flora are not

uncommon.

GENERAL REMARKS ON FOSSIL VEGETABLES.

173. The design of this book will not allow of a more extended account of fossil plants; but before leaving the subject, we shall make a few remarks on the foregoing synopsis, and especially with respect to the geological periods of the ancient or Fossil Flora.

It appears from the catalogue of fossil vegetables, published by Mr. Morris in 1843, that in the British strata alone there had been discovered above six hundred species. Among these, only two of the grasses had been detected, these being of the genus Poa, a very common grass in most parts of the world. Possibly it may be owing to their diminutive size that so few of this tribe have occurred, though many ferns, little larger, are found in every coal mine.

From the data hitherto obtained the most eminent botanists, Sternberg, Brongniart and Lindly, consider that the Floras of the ancient world would constitute three distinct periods or epochs.

First Epoch.-The first comprehends the earliest strata in which traces of vegetables appear, and includes the Carboniferous, (131.) The plants of this epoch, as we have already shown, consist of fuci, or sea-weeds, and other cellular tribes; ferns of various kinds and in great abundance; coniferous trees, related to species in warm climates; of palms and other monocotyledons; gigantic lycopodia, or club-mosses; and large trees of unknown tribes, as Sigillaria and Stigmaria, in profusion. In this Flora the tree ferns predominate, constituting nearly twothirds of the whole known species, and the general type the vegetation is analogous to that of tropical climates.

of

Second Epoch.-This extends from the Saliferous or New Red, (130,) to the Chalk inclusive, and is characterized by the appearance of many species of the Cycadeæ, Zamiæ, and Coniferæ, while the proportions of the ferns are much less than in the preceding period, and the Lycopodiums, and Calamites of the Carboniferous strata, are absent. A Flora of these remains would be analogous to that of the coasts of New-Holland and the Cape of Good Hope.

Third Epoch.-The third epoch is that of the Tertiary, (125,) in which the Dicotyledonous tribes appear in great numbers: the Cycadeæ are very rare; the ferns are comparatively few; and the Coniferæ more numerous. Palms and intertropical plants are found associated with the existing European forest trees, as the elm, willow,

What are the three epochs of fossil Botany? What plants form the Flora of the first epoch? What of the second? What of the third?