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possibly at some other places on the coast. The beds rest directly and apparently conformably on the Upper Cretaceous, and have afforded only eleven species of plants. Magnolia is represented by two species, Laurus by two, Platanus by two, and one of these said to be identical with a species found by Lesquereux in the Laramie,* Vibu m, Juglans, Quercus, each by one species; the ubiquitous Sequoias by S. Langsdorffii. This is pretty clearly a Lower Laramie flora.
5. The Atanekerdluk series, consisting of shaly beds, with limestone intercalated between great sheets of basalt, much like the Eocene of Antrim and the Hebrides. These beds have yielded 187 species, principally in bands and concretions of siderite, and often in a good state of preservation. They are referred to the Lower Miocene, but, as explained in the text, the flora is more nearly akin to that of the Eocene of Europe and the Laramie of America. The animal fossils are chiefly fresh-water shells. Onoclea sensibilis, several conifers, as Taxites Olriki, Taxodium distichum, Glyptostrobus Europæus, and Sequoia Langsdorffii, and 42 of the dicotyledons are recognised as found also in American localities. Of these, a large proportion of the more common species occur in the Laramie of the Mackenzie River and elsewhere in northwest Canada, and in the western United States. It is quite likely also that several species regarded as distinct may prove to be identical.
It would seem that throughout the whole thickness of these Tertiary beds the flora is similar, so that it is probable it belongs altogether to the Eocene rather than to the Miocene.
No indication has been observed of any period of cold intervening between the Lower Cretaceous and the top of the Tertiary deposits, so that, in all the vast period which these formations represent, the climate of Greenland would seem to have been temperate. There is, however, as is the case farther south, evidence of a gradual diminution of temperature. In the Lower Cretaceous the probable mean annual temperature in latitude 71° north is stated as 21° to 22° centigrade, while in the early Tertiary it is estimated at 12° centigrade. Such temperatures, ranging from 71° to 53° of Fahrenheit, represent a marvellously warm climate for so high a latitude. In point of fact, however, the evidence of warm climates in the arctic regions, in the Palæozoic as well as in the Mesozoic and early Tertiary, should perhaps lead us to conclude that, relatively to the whole of geological time, the present arctic climate is unusually severe, and
* Viburnum marginatum of Lesquereux.
that a temperate climate in the arctic regions has throughout geological time been the rule rather than the exception.
III.—MINERALISATION OF FOSSIL PLANTS.
The state of preservation of fossil plants has been referred to incidentally in several places in the text; but the following more definite statements may be of service to the reader.
I. Organic remains imbedded in aqueous deposits may occur in an unchanged condition, or only more or less altered by decay. This is often the case with such enduring substances as bark and wood, and even with leaves, which appear as thin carbonaceous films when the layers containing them are split open. In the more recent deposits such remains occur little modified, or perhaps only slightly changed by partial decay of their more perishable parts. In the older formations, however, they are usually found in a more or less altered condition, in which their original substance has been wholly or in part changed into coaly, or bituminous, or anthracitic or graphitic matter, so that leaves are sometimes represented by stains of graphite, as if drawn on stone with a lead-pencil. Yet even in this case some portion of the original substance remains, and without any introduction of foreign material.
II. On the other hand, such remains are often mineralised by the filling of their pores or the replacement of their tissues with mineral matter, so that they become hard and stony, and sometimes retain little or nothing of their original substance. The more important of these changes, in so far as they affect fossil plants, may be arranged under the following heads:
(a) Infiltration of mineral matter which has penetrated the pores of the fossil in a state of solution. Thus the pores of fossil wood are often filled with calcite, quartz, oxide of iron, or sulphide of iron, while the woody walls of the cells and vessels remain in a carbonised state, or converted into coaly matter. When wood is preserved in this way it has a hard and stony aspect; but we can sometimes dissolve away the mineral matter, and restore the vegetable tissue to a condition resembling that before mineralisation. This is especially the case when calcite is the mineralising substance. We sometimes find, on microscopic examination, that even cavities so small as those of vegetable cells and vessels have been filled with successive coats of different kinds of mineral matter.
(6) Organic matters may be entirely replaced by mineral substances. In this case the cavities and pores have been first filled, and then—the walls or solid parts being removed by decay or solution-mineral matter, either similar to that filling the cavities, or differing in colour or composition, has been introduced. Silicified wood often occurs in this condition. In the case of silicified wood, it sometimes happens that the cavities of the fibers have been filled with silica, and the wood has been afterward removed by decay, leaving the casts of the tubular fibers as a loose filamentous substance. Some of the Tertiary coniferous woods of California are in this state, and look like asbestus, though they show the minute markings of the tissue under the microscope. In the case of silicified or agatized woods, it would seem that the production of carbon dioxide from the decaying wood has caused the deposition of silica in its place, from alkaline solutions of that substance, and thus the carbon has been replaced, atom by atom, by silicon, until the whole mass has been silicified, yet retaining perfectly its structure.
(C) The cavities left by fossils which have decayed may be filled with clay, sand, or other foreign matter, and this, becoming subsequently hardened into stone, may constitute a cast of the fossils. Trunks of trees, roots, &c., are often preserved in this way, appearing as stony casts, often with the outer bark of the plant forming a carbonaceous coating on their surfaces. In connection with this state may be mentioned that in which, the wood having decayed, an entire trunk has been flattened so as to appear merely as a compressed film of bark, yet retaining its markings; and that in which the whole of the vegetable matter having been removed, a mere impression of the form remains.
Fossils preserved in either of the modes, (a) or (b), usually show more or less of their minute structures under the microscope. These may be observed :-(1) By breaking off small splinters or flakes and examining them, either as opaque or as transparent objects. (2) By treating the material with acids, so as to dissolve out the mineral matters, or portions of them. This method is especially applicable to fossil woods mineralised with calcite or pyrite. (3) By grinding thin sections. These are first polished on one face on a coarse stone or emery hone, and then on a fine hone, then attached by the polished face to glass slips with a transparent cement or Canada balsam, and ground on the opposite face until they become so thin as to be translucent. In most cities there are lapidaries who prepare slices of this kind; but the amateur can readily acquire the art by a little practice, and the necessary appliances can be obtained through dealers in minerals or in microscopic materials. Very convenient cutting and polishing machines, some of them quite small and portable, are now made for the use of amateurs. In the case of exogenous woods, three sections are necessary to exhibit the whole of the structures. One of these should be transverse and two longitudinal, the latter in radial and tangential planes.
IV.-GENERAL WORKS ON PALÆOBOTANY.
In the text frequent reference has been made to special memoirs and reports on the fossil plants of particular regions or formations, There are, however, some general books, useful to students, which may be mentioned here. Perhaps the most important is Schimper's " Traité de Paléontologie Végétale.” Very useful information is also contained in Renault's “ Cours de Botanique Fossile,” and in Balfour's “ Introduction to Palæontological Botany,” and Nicholson's “ Palæontology.” Unger's “Genera et Species,” Brongniart's “ Histoire des Végétaux Fossiles,” and Lindley and Hutton's “ Fossil Flora,” are older though very valuable works. Williamson's “Memoirs,” in the “ Philosophical Transactions,” have greatly advanced our knowledge of the structures of Palæozoic plants. Lastly, the “ Palæophytology” of Schenk, now in course of publication in German and French, in connection with Zittel's “ Palæontology,” is an important addition to manuals of the subject.
Bovey Tracey, Plants of, 226.
Acer, 228. Acrogens, 6. Agassiz, Prof., 16. Alaska, Flora of, 245. Algæ, real and spurious, 26, 230. Amboy clays, Flora of, 203. America, Cretaceous of, 190. Angiosperms, 6. Annularia, 122. Anogens, 6. Antholithes, 132. Aporoxylon, 25. Araucarioxylon, 148. Araucarites, 134. Archæocalamites, 170, Archæopteris, 77, 85. Arctic origin of plants, 221, 238. Arthrophycus, 30. Arthrostigma, 67. Asterophyllites, 78, 122, 170. Asteropteris, 77, 85. Astropolithon, 30. Atané, Plants of, 242, 281. Atanekerdluk, Plants of, 283. Australia, Palæozoic flora of, 147.
Tertiary flora of, 217.
Calamites, 77, 123, 166.
Carboniferous of, 110.
Pleistocene of, 227.
of Southern Hemisphere, 147.
plants, 225, 269.
of Carboniferous, 138.
Bauhinia, 204. Bear Island, 241. Betula, 198. Bilobites, 28.