Chapter III: Part 3

True Exogenous trees exist in the coal-fields both of England and Scotland, as at Lennel Braes and Allan Bank, in Berwickshire; High-Heworth, Fellon, Gateshead, and Wideopen, near Newcastle-upon-Tyne; and in quarries to the west of Durham; also in Craigleith quarry, near Edinburgh, and in the quarry at Granton, now under water. In the latter localities they lay diagonally athwart the sandstone strata, at an angle of about 30°, with the thicker and heavier part of their trunks below, like snags in the Mississippi. From their direction we infer that they have been drifted by a stream which has flowed from nearly north-east to south-west. At Granton, one of the specimens exhibited roots. In other places the specimens are portions of stems, one of them 6 feet in diameter by 61 feet in length, and another 4 feet in diameter by 70 feet in length. These Exogenous trees are Gymnosperms, having woody tissue like that of Coniferæ. We see under the microscope punctated woody tissue, the rows of disks being usually two, three, or more, and alternating. They seem to be allied in these respects to Araucaria and Eutassa (Fig. 61, p. 74) of the present flora. Araucarioxylon or Pinites Withami (Fig. 49) is one of the species found in Craigleith quarry; the concentric layers of the wood are obsolete; there are 2, 3, or 4 rows of disks on the wood, and 2-4 rows of small cells in the medullary rays. Along with it there have also been found Dadoxylon medullare, with inconspicuous zones, 2, 3, and 4 rows of disks, and 2-5 series of rows of cells in the rays. Pissadendron antiquum (Pitus antiqua) having 4-5 series of cells in the medullary rays, and P. primævum (Pitus primæva), with 10-15 series of cells in the medullary rays, occur at Tweedmill and Lennel Braes in Berwickshire; Peuce Withami (Fig. 1, p. 3) at Hilltop, near Durham, and at Craigleith. Sternbergia is considered by Williamson as a Dadoxylon, with a discoid pith like that seen now-a-days in the Walnut, Jasmine, and Cecropia peltata, as well as in some species of Euphorbia.[14] Sternbergia approximata is named by him Dadoxylon approximatum. Hooker believes from the structure of Trigonocarpum (Fig. 50) that it is a coniferous fruit nearly allied to Salisburia (Trans. Roy. Soc. 1854). Several species of Trigonocarpum occur in the Carboniferous rocks, such as T. olivæforme from Bolton (Plate II. Fig. 5), and T. sulcatum from Wardie, near Edinburgh (Plate II. Fig. 6). Noeggerathia and a few other plants, such as Flabellaria and Artisia, are referred by Brongniart to Cycadaceæ. Flabellaria borassifolia, according to Peach, has leaves like Yucca. Noeggerathia has pinnate leaves, cuneiform leaflets, sometimes fan-shaped; the veins arise from the base of the leaflets, are equal in size, and either remain simple or bifurcate, the nervation (venation) being similar to that of some Zamias.

The fossils of this period, referred to as Antholithes,[15] have just been shown by Mr. Carruthers to be the inflorescence of Cardiocarpum (Geol. Mag. Feb. 1872), and he proposes to set aside the former name, confining it to the tertiary fossils to which it was originally given by Brongniart, and to use the latter name. The main axis of the inflorescence is simple, stout, and marked externally with interrupted ridges. The axis bears in a distichous manner sub-opposite or alternate bracts of a linear-lanceolate form and with decurrent bases. In the axils of the bracts were developed flower-like leaf-bearing buds, and from them proceeded three or four linear pedicels, which terminated upwards in a somewhat enlarged trumpet-shaped apex. To this enlarged articulating surface was attached the fruit, to which has been given the generic name Cardiocarpum[16] (Fig. 51). The place of attachment is indicated by the short straight line which separates the cordate lobes at the base of the fruit. The fruit is flattish, broadly ovate, with a cordate base and sub-acute apex. It consists of an outer pericarp, inclosing an ovate-acute seed. That the pericarp was of some thickness, and formed probably a sub-indurated rind, is shown by a specimen preserved in the round, and figured (Fig. 53 _a_). The pericarp is open at the apex; and the elongated tubular apex of the spermoderm passes up to this opening. The seed forms a distinct swelling in the centre of the fruit, and a slight ridge passes up the middle to the base of the apical opening.

[Sidenote: Fig. 51. _Cardiocarpum Lindleyi_, Carr. Fig. 52. Do., Coal-measures, Falkirk.]

These fossils are believed to be an extinct form of Gymnosperms. Two species have been described, of both of which we are able to give figures. The first figure is from the specimens collected by Mr. Peach at Falkirk. It is Cardiocarpum Lindleyi (Figs. 51, 52); it has a primary axis with sub-opposite axillary axes, bearing four to six lanceolate leaves and three or four pedicels. Primary bracts short and arcuate. Fruit ovate-cordate, with an acute bifid apex, and a ridge passing up the middle of the fruit.

[Sidenote: Fig. 53. _Cardiocarpum anomalum_ (Carr.), natural size: with separate fruit (_a_), twice natural size--Coal-measures, Coalbrookdale.]

The second species is Cardiocarpum anomalum (Fig. 53) from Coalbrookdale; it has a primary axis with alternate or sub-opposite axillary axes, slender and elongated, bearing many linear leaves, and several slender pedicels; primary bracts long, slender, and straight; fruits small, margined. The somewhat magnified separate fruit (_a_) shows the thickness of the pericarp and the enclosed seed.

[Sidenote: Fig. 54. _Pothocites Grantoni_, Paterson. _a_, Spike natural size; _b_, Portion of spike magnified; _c_, Perianth, 4-cleft, magnified.]

In the bituminous shale at Granton, near Edinburgh, Dr. Robert Paterson discovered in 1840 a peculiar fossil plant, which he called Pothocites Grantoni (Fig. 54, _a_). It is figured in the Transactions of the Edinburgh Botanical Society, vol. i. March 1840. It is a spike covered by parallel rows of flowers (Fig. 54, _b_), each apparently with a 4-cleft calyx (Fig. 54, _c_). It was supposed to be allied to Potamogeton or Pothos, more probably to the latter. In that case it must be referred to the natural order Araceæ. The original specimen is deposited in the museum at the Royal Botanic Garden, Edinburgh.

Our knowledge of the real state of the vegetation of the earth when coal was formed must be very limited, when we reflect how seldom the fructification of coniferous trees has been met with in the coal-measures. A very doubtful fragment, supposed to be a cone, is given in Lindley and Hutton's work, under the title of Pinus anthracina; but it is believed by Carruthers to be a fragment of a Lepidodendroid branch. Lyell never saw a fossil fir-cone of the Carboniferous epoch, either in the rocks or museums of North America or Europe. Bunbury never heard of any other example than that noticed by Lindley and Hutton. Principal Dawson is disposed to think that the suberin of cork, of epidermis in general, and of spore-cases in particular, is a substance so rich in carbon that it is very near to coal, and so indestructible and impermeable to water, that it contributes more largely than anything else to the mineral. Sir Charles Lyell remarks--"To prevent ourselves, therefore, from hazarding false generalisations, we must ever bear in mind the extreme scantiness of our present information respecting the flora of that peculiar class of stations to which, in the Palæozoic era, the coal-measures probably belonged. I have stated elsewhere my conviction that the plants which produced coal were not drifted from a distance, but nearly all of them grew on the spot where they became fossil. They constituted the vegetation of low regions, chiefly the deltas of large rivers, slightly elevated above the level of the sea, and liable to be submerged beneath the waters of an estuary or sea by the subsidence of the ground to the amount of a few feet. That the areas where the carboniferous deposits accumulated were low, is proved not only by the occasional association of marine remains, but by the enormous thickness of strata of shale and sandstone to which the seams of coal are subordinate. The coal-measures are often thousands of feet, and sometimes two or three miles, in vertical thickness, and they imply that for an indefinite number of ages a great body of water flowed continuously in one direction, carrying down towards a given area the detritus of a large hydrographical basin, draining some large islands or continents, on the margins of which the forests of the coal period grew. If this view be correct, we can know little or nothing of the upland flora of the same era, still less of the contemporaneous plants of the mountainous or alpine regions. If so, this fact may go far to account for the apparent monotony of the vegetation, although its uniform character may doubtless be in part owing to a greater uniformity of climate then prevailing throughout the globe. Mr. Bunbury has successfully pointed out that the peculiarity of the carboniferous climate consisted more in the humidity of the atmosphere and the absence of cold, or rather the equable temperature preserved in the different seasons of the year, than in its tropical heat; but we must still presume that colder climates existed at higher elevations above the sea."

The plants of the coal-measures are evidently terrestrial plants. Brongniart agrees with Lyell in thinking that the layers of coal have in general accumulated in the situation where the plants forming them grew. The remains of these plants covered the soil in the same way as layers of peat, or the vegetable mould of great forests. In a few instances, however, the plants may have been transported from a distance, and drifted into basins. Phillips is disposed to think that this was the general mode of formation of coal-basins. He is led to this conclusion by observing the fragmentary state of the stems and branches, the general absence of roots, and the scattered condition of all the separable organs. Those who support the drift theory, look on the coal plants as having been swept from the land on which they grew by watery currents at different times, and deposited in basins and large sea-estuaries, and sometimes in lakes. The snags in the Mississippi, the St. Lawrence, and other large rivers, are given as instances of a similar drifting process.

The vegetation of the coal epoch seems to resemble most that of islands in the midst of vast oceans, and the prevalence of ferns indicates a climate similar to that of New Zealand in the present day. In speaking of the island vegetation of the coal epoch, Professor Ansted remarks (Ancient World, p. 88)--"The whole of the interior of the islands may have been clothed with thick forests, the dark verdure of which would only be interrupted by the bright green of the swamps in the hollows, or the brown tint of the ferns covering some districts near the coasts. The forests may have been formed by a mixture of several different trees. We would see then, for instance, the lofty and widely-spreading Lepidodendron, its delicate feathery fronds clothing, in rich luxuriance, branches and stems, which are built up, like the trunk of the tree-fern, by successive leafstalks that have one after another dropped away, giving by their decay additional height to the stem, which might at length be mistaken for that of a gigantic pine. There also should we find the Sigillaria, its tapering and elegant form sustained on a large and firm basis--enormous matted roots, almost as large as the trunk itself, being given off in every direction, and shooting out their fibres far into the sand and clay in search of moisture. The stem of this tree would appear like a fluted column, rising simply and gracefully without branches to a great height, and then spreading out a magnificent head of leaves like a noble palm-tree. Other trees, more or less resembling palms, and others like existing firs, also abounded, giving a richness and variety to the scene; while one gigantic species, strikingly resembling the Norfolk Island pine, might be seen towering a hundred feet or more above the rest of the forest, and exhibiting tier after tier of branches richly clothed with its peculiar pointed spear-like leaves, the branches gradually diminishing in size as they approach the apex of a lofty pyramid of vegetation. Tree-ferns also in abundance might there be recognised, occupying a prominent place in the physiognomy of vegetation, and dotted at intervals over the distant plains and valleys, the intermediate spaces being clothed with low vegetation of more humble plants of the same kind. These we may imagine exhibiting their rich crests of numerous fronds, each many feet in length, and produced in such quantity as to rival even the palm-trees in beauty. Besides all these, other lofty trees of that day, whose stems and branches are now called Calamites, existed chiefly in the midst of swamps, and bore their singular branches and leaves aloft with strange and monotonous uniformity. All these trees, and many others that might be associated with them, were, perhaps, girt round with innumerable creepers and parasitic plants, climbing to the topmost branches of the most lofty amongst them, and relieving, in some measure, the dark and gloomy character of the great masses of vegetation."

Hugh Miller remarks--"The sculpturesque character of the nobly-fluted Sigillarias was shared by not a few of its contemporaries. Ulodendrons, with their rectilinear rows of circular scars, and their stems covered with leaf-like carvings, rivalled in effect the ornately relieved torus of a Corinthian column. Favularia, Halonia, many of the Calamites, and all the Lepidodendrons, exhibited the most delicate sculpturing. In walking among the ruins of this ancient flora, the palæontologist almost feels as if he had got among the broken fragments of Italian palaces erected long years ago, when the architecture of Rome was most ornate, and every moulding was roughened with ornament; and in attempting to call up in fancy the old Carboniferous forests, he has to dwell on this peculiar feature as one of the most prominent; and to see in the multitude of trunks darkened above by clouds of foliage that rise upon him in the prospect, the slender columns of an older Alhambra, roughened with arabesque tracery and exquisite filigree work."

_FLORA OF THE PERMIAN EPOCH._

[Sidenote: Figs. 55 and 56. _Walchia piniformis_, Sternb., a common species in the Permian rocks of Europe. Fig. 55. Plant with leaves and fructification. Fig. 56. Fructification, natural size.]

The nature of the vegetation during the Permian period, which is associated with the Carboniferous, under the reign of Acrogens, has been extensively illustrated by Goeppert. Brongniart has enumerated the fossils in three different localities, which he refers doubtfully to this period. 1. The flora of the bituminous slates of Thuringia, composed of Algæ, Ferns, and Coniferæ. 2. Flora of the Permian sandstones of Russia, comprehending Ferns, Equisetaceæ, Lycopodiaceæ, and Noeggerathiæ. 3. Flora of the slaty schists of Lodève, composed of Ferns, Asterophyllites, and Coniferæ. The genera of Ferns here met with are those found in the Carboniferous epoch; the Gymnosperms are chiefly species of Walchia and Noeggerathia (the latter is supposed by Schimper to be a Cycad); Lepidodendron elongatum, Calamites gigas, and Annularia floribunda, are also species of this period. Walchia is a conifer characteristic of the Permian epoch, of which there are eight species described (Figs. 55 and 56). It has a single seed to each scale of the cone, and two kinds of leaves, the one short and imbricated, the other long and spreading. Among the plants of the Permian formation Goeppert enumerates the following:[17]--Equisetites contractus, Calamites Suckowi, C. leioderma, Asterophyllites equisetiformis, A. elatior, Huttonia truncata, H. equisetiformis, many species of Psaronius, one of the filicoid plants, Hymenophyllites complanatus, Sphenopteris crassinervia, Sagenopteris tæniæfolia, Neuropteris imbricata, and many other species of these genera; several species of Odontopteris, Callipteris, Cyclopteris, Dioonopteris, Cyatheites, Alethopteris, Noeggerathia, Cordaites, Anthodiopsis, Dictyothalamus, Calamodendron, Arthropitys; besides species of Sigillaria, Stigmaria, and Lepidodendron. Various fruits are also mentioned, under the names of Rhabdocarpum, Cardiocarpum, Acanthocarpum, Trigonocarpum, and Lepidostrobus.

FOSSIL FLORA OF THE SECONDARY OR MESOZOIC PERIOD.

REIGN OF GYMNOSPERMS.

[Sidenote: Fig. 57. _Pinus sylvestris_, Scotch Fir.

Fig. 58. _Abies excelsa_, common Spruce Fir of northern Europe.

Fig. 59. _Larix Europæa_, the Larch, indigenous on the Alps of middle Europe.

Fig. 60. _Cedrus Libani_, Cedar of Lebanon.]

The Gymnospermous plants of the present day are included in two natural orders, Coniferæ and Cycadaceæ. Under Coniferæ are enumerated the various species of Pine (Fig. 57), Spruce (Fig. 58), Larch (Fig. 59), Cedar (Fig. 60), Eutassa, Araucaria (Fig. 61), Sequoia, Cryptomeria, Taxodium, Cypress, Juniper (Fig. 70), Salisburia, Dacrydium, Yew (Fig. 71), etc.

[Sidenote: Fig. 61. _Araucaria excelsa_, called also _Altingia_ or _Eutassa_ or _Eutacta excelsa_, Norfolk Island Pine.

Fig. 62. Woody tubes of fir, with single rows of discs.

Fig. 63. Woody tubes of fir, with double rows of discs, which are opposite to each other.

Fig. 64. Woody tubes of _Araucaria excelsa_, with double and triple rows of discs, which are alternate.

Fig. 65. Longitudinal section of the stem of a Gymnosperm, showing tubes of wood marked with punctations in one or more rows, and a medullary ray composed of cells running across the pleurenchyma.]

[Sidenote: Fig. 66. Linear leaves of _Pinus Strobus_, Weymouth Pine, in a cluster of five, with scaly sheath at the base.

Fig. 67. Cone of _Pinus sylvestris_, Scotch Fir.

Fig. 68. Cone of _Cupressus sempervirens_, common Cypress.

Fig. 69. Scale, _s_, of mature cone of _Pinus sylvestris_, with two naked winged seeds, _m m_, at its base; _ch_ marks the chalaza, _m_ the micropyle.]

The Coniferæ of the present day are distinguished as resinous trees or shrubs with punctated woody tissue (Figs. 62, 63, 64, 65), linear acerose or lanceolate parallel-veined leaves, sometimes clustered, and having a membranous sheath at the base (Fig. 66). Male flowers in deciduous catkins; female flowers in cones (Figs. 67, 68). The seeds are considered by most botanists as being naked, _i.e._ not contained in a true pistil (Fig. 69). Some of the conifers have a succulent cone, as the juniper (Fig. 70), and the yew (Figs. 71-73) has a succulent mass covering a single naked seed (Fig. 73). The yew also has its pleurenchyma marked both with punctations and spiral fibres. The arrangement of the punctations in the Coniferæ gives characters which enable us to classify the woods into groups that have some relation to the genera established from the reproductive organs (see Figs. 62-65).

[Sidenote: Fig. 70. Fruiting branch of _Juniperus communis_, common Juniper, with linear acerose leaves and succulent cones.

Fig. 71. Branch of _Taxus baccata_, common Yew.

Fig. 72. Male flower of Yew, with bracts at the base.

Fig. 73. Fruit of Yew, consisting of a single naked seed partially covered by a succulent receptacle.]

The natural order Cycadaceæ is not so largely represented at the present day as it was during the Mesozoic epoch. Among the genera of the present day are Cycas (Fig. 74), Zamia, Macrozamia, Encephalartos (Fig. 75), Dion, Stangeria, etc. They are small palm-like trees or shrubs, with unbranched stems, occasionally dichotomous, marked with leaf-scars, and having large medullary rays along with pitted woody tissue. The leaves are pinnate, except in Bowenia, which has a bipinnate leaf. Males in cones. Females consisting of naked ovules on the edges of altered leaves, or on the inferior surface of the peltate apex of scales.[18]

_FLORA OF THE TRIAS AND LIAS EPOCHS._

[Sidenote: Fig. 74. _Cycas revoluta_, one of the false Sago-plants found in Japan.

Fig. 75. _Encephalartos (Zamia) pungens_, another starch-yielding Cycad.]

In this reign the Acrogenous species are less numerous; the Gymnosperms almost equal them in number, and ordinarily surpass them in frequency. There are two periods in this reign, one in which Coniferæ predominate, while Cycadaceæ scarcely appear; and another in which the latter family preponderates as regards the number of species, and the frequency and variety of generic forms. Cycadaceæ occupied a more important place in the ancient than in the present vegetable world. They extend more or less from the Trias formation up to the Tertiary. They are rare in the Grès bigarré or lower strata of the Triassic system. They attain their maximum in the Lias and Oolite, in each of which upwards of 40 species have been enumerated, and they disappear in the Tertiary formations. Schimper describes 13 genera of fossil Zamiæ, and about 20 Cycadeæ. He thinks that Trigonocarpum (15 species), Rhabdocarpum (24 species), Cardiocarpum (21 species), and Carpolithes (9 species), are all fruits of Cycadeæ. Many supposed fossil Cycads are looked upon by Carruthers as Coniferæ. Zamia macrocephala, or Zamites macrocephalus, or Zamiostrobus macrocephalus, is called by him Pinites macrocephalus; Zamia ovata, or Zamites ovatus, or Zamiostrobus ovatus, is Pinites ovatus; Zamia Sussexiensis is Pinites Sussexiensis. Among other species of Pinites noticed by Carruthers are Pinites oblongus, P. Benstedi, P. Dunkeri, P. Mantellii, P. patens, P. Fittoni, P. elongatus. It is important to notice that in an existing Cycad called Stangeria paradoxa the veins of the pinnæ rise from a true midrib and fork, characters which render untenable the distinction usually relied upon between the foliage of Ferns and Cycads.

[Sidenote: Fig. 76. _Schizoneura heterophylla_, one of the fossil Coniferæ of the Triassic system.]

In Brongniart's Vosgesian period, the Grès bigarré, or the Red Sandstones and Conglomerates of the Triassic system, there is a change in the flora. Sigillarias and Lepidodendrons disappear, and in their place we meet with Gymnosperms, belonging to the genera Voltzia, Haidingera, Zamites, Ctenis, Æthophyllum, and Schizoneura (Fig. 76). The genus Voltzia is confined to the Trias, and though a true conifer, it is not easy to correlate it with any living form. It is apparently Abietineous, having two seeds to each scale, but they are placed on the dilated upper portion of the scale. The leaves are of two kinds, the one broad and short, and the other at the tops of the branches long and linear. Species of Neuropteris, Pecopteris, and other acrogenous coal genera are still found, along with species of Anomopteris and Crematopteris--peculiar Fern-forms, which are not found in later formations. Stems of arborescent Ferns are more frequent than in the next period.

The Jurassic period of Brongniart embraces the Keupric period or variegated marls of the Triassic system, the Liassic epoch, the Oolitic and the Wealden. The flora of the Keupric epoch differs from that of the Grès bigarré of the Vosges. The Acrogens are changed as regards species, and frequently in their genera. Thus we have the genera Camptopteris, Sagenopteris, and Equisetum. Among Gymnosperms, the genera Pterophyllum and Taxodites occur.

[Sidenote: Figs. 77 to 81. Cycadaceæ of the Jurassic epoch of Brongniart, and of the Oolite. Fig. 77. Zamites, one of the fossil Cycadaceæ. Fig. 78. _Pterophyllum Pleiningerii_, leaf of a fossil Cycad. Fig. 79. _Nilssonia compta_ (_Pterophyllum comptum_ of Lindley and Hutton), from the Oolite of Scarborough. Lower part of the pinnatifid leaf, with blunt almost square divisions. There are numerous veins, slightly varying in thickness; while in Pterophyllum there are numerous veins of equal thickness, in Cycadites there is a solitary vein forming a thick midrib. Fig. 80. _Palæozamia pectinata_ (_Zamia pectinata_ of Brongniart, and Lindley and Hutton), a pinnated leaf, with a slender rachis. The pinnæ are linear, somewhat obtuse, with slender equal ribs. It is found in the Oolite of Stonesfield (Lindley and Hutton).]

In the Lias the essential characters of the flora are the predominance of Cycadaceæ, in the form of species of Cycadites, Otozamites, Zamites (Fig. 77), Ctenis, Pterophyllum (Fig. 78), and Nilssonia (Fig. 79), Palæozamia (Fig. 80), and the existence among the Ferns of many genera with reticulated venation, such as Camptopteris and Thaumatopteris, some of which began to appear at the Keupric epoch. Coniferous genera, as Brachyphyllum (Fig. 81), Taxodites, Palissya, and Peuce, are found. In the Lias near Cromarty, Miller states that he found a cone with long bracts like those of Pinus bracteata.

_FLORA OF THE OOLITIC EPOCH._

In the Oolitic epoch the flora consists of numerous Cycadaceæ and Coniferæ, some of them having peculiar forms. Its distinctive characters are, the rarity of Ferns with reticulated venation, which are so numerous in the Lias, the frequency of the Cycadaceous genera Otozamites and Zamites, which are most analogous to those now existing; the occurrence of a remarkable group presenting very anomalous structure in their organs of reproduction, to which Carruthers has given the name of Williamsonia; and the diminution of Ctenis, Pterophyllum, Palæozamia, and Nilssonia, genera far removed from the living kinds; and lastly, the greater frequency of the coniferous genera, Brachyphyllum and Thuites, which are much more rare in the Lias. In the Scottish Oolite at Helmsdale, Miller detected about 60 species of plants, including Cycadaceæ and Coniferæ, with detached cones, and Fern-forms resembling Scolopendrium. He also discovered a species of Equisetum, and what he supposed to be a Calamite.

[Sidenote: Fig. 81. _Brachyphyllum mammillare_, a Coniferous plant of the Oolitic system, Yorkshire.

Fig. 82. _Equisetum columnare_, a fossil species of the Oolite of Yorkshire.]

[Sidenote: Fig. 83. _Araucarites sphærocarpus_, Carr., found in the inferior Oolite at Bruton, Somersetshire.

Fig. 84. Termination of a scale of _Araucarites sphærocarpus_, Carr.

Fig. 85. Section of a scale of _Araucarites sphærocarpus_, Carr., showing the size and position of the seed.]

[Sidenote: Fig. 86. The _Dirt-bed_ of the Island of Portland, containing stumps of fossil Cycadaceæ in an erect position.

Fig. 87. _Cycadoidea megalophylla_ (_Mantellia nidiformis_ of Brongniart), a subglobose depressed trunk, with a concave apex, and with the remains of the petioles disposed in a spiral manner, the markings being transversely elliptical. It is found in the Oolite of the Island of Portland, in a silicified state.]

There is an absence of true coal-fields in the secondary formations generally; but in some of the Oolitic series, as in the lower Oolite at Brora, in Sutherlandshire, and in the north-east of Yorkshire, and the Kimmeridge clay of the upper Oolite, near Weymouth, there are considerable deposits of carbonaceous matter, sometimes forming seams of coal which have been worked for economic purposes.[19] Some suppose that the Brora coal was formed chiefly by Equisetum columnare (Fig. 82). In the sandstones and shales of the Oolitic series, especially in the lower Oolite of the north of England, as at Whitby and Scarborough, as well as in Stonesfield slate, the Portland Crag of the middle, and the Portland beds of the upper Oolite, numerous fossil plants are found. Peuce Lindleyana is one of the Coniferæ of the lower Oolite. Beania (Plate II. Fig. 2) is a Cycadaceous fossil from the Oolite of Yorkshire (Carruthers, Geol. Mag. vi. 91). Araucarites sphærocarpus (Figs. 83, 84, 85) is found in the inferior Oolite, and separate scales of Araucarian fruits occur in the Oolitic shales of Yorkshire (Araucarites Phillipsii, Plate II. Fig. 11), and in the "slate" at Stonesfield (A. Brodiei, Plate II. Fig. 10). The upper Oolite at Portland contains an interesting bed, about a foot in thickness, of a dark brown substance. This is the _Dirt-bed_ (Fig. 86) made up of black loam, which, during the Purbeck period, formed a surface soil which was penetrated by the roots of trees, fragments of whose stems are now found in it fossilised. These consist of an assemblage of silicified stumps or stools of large trees, from 1-3 feet high, standing in their original position, with the roots remaining attached to them, and still penetrating the earth in which they grew. Besides the erect trunks many stems have been broken and thrown down, and are buried in a horizontal position in the bed. They belong to Coniferæ and Cycadaceæ. One of these is Mantellia nidiformis, shown in Fig. 87. Carpolithes conicus and C. Bucklandi are fruits found in the Oolite. Some look upon them as fruits of palms.

[Sidenote: Fig. 88. _Kaidacarpum ooliticum_, Carr., fruit of a fossil allied to Pandanaceæ, from the great Oolite near Northampton.

Fig. 89. _Pandanus odoratissimus_, Screw-pine, with adventitious roots.]

Several species of Pandanaceous fruits have been found in Oolitic strata. Buckland described one of them as Podocarya, which is remarkable, as it consists of a single but many-seeded drupe. To another form, more nearly allied to the existing plants, Carruthers has given the name Kaidacarpum, and has described three species. These fruits are made up of a large number of single-seeded drupes. The species figured (Fig. 88) is from the great Oolite, near Northampton. In Fig. 89 a representation is given of one of the Pandanaceæ, the screw-pines of the present day.

_FLORA OF THE WEALDEN EPOCH._

[Sidenote: Fig. 90. Fossil Wood, _Abietites Linkii_. A Coniferous plant from the Wealden, showing punctated woody tissue and medullary rays.]

The flora of the Wealden epoch is characterised in the south of England by the abundance of the fern called Lonchopteris Mantellii, and in Germany by the predominance of the Conifer denominated Abietites Linkii (Fig. 90), and the presence of Araucarites Pippingfordensis, as well as by numerous Cycadaceæ, such as species of Cycadites, Zamites, Pterophyllum, Mantellia, Bucklandia, and a remarkable genus having a fleshy fruit, and related to the ordinary Cycadaceæ as Taxus is to the other Coniferæ, which has been fully described in the Linn. Trans., under the name of Bennettites (Plate II. Fig. 3). In the Wealden at Brook Point, Isle of Wight, Cycads have been detected allied to Encephalartos. The fruits of them are described by Carruthers as Cycadeostrobus. He describes the following species:--Cycadeostrobus ovatus (Plate II. Fig. 1), C. truncatus, C. tumidus, C. elegans, C. Walkeri, C. sphæricus, in the Oxford clay of Wiltshire; C. primævus in the inferior Oolite at Burcott Wood and Livingston, and C. Brunonis. Mantell states that he has found 40 or 50 fossil cones in the Wealden of England; they belong either to the genus Cycadeostrobus or to the pines mentioned below as occurring in the Wealden. The Wealden fresh-water formation terminates the reign of Gymnosperms. Carruthers gives the following list of the remains of Coniferæ which have been found in the secondary strata of Britain, excluding the Trias:--

Upper Chalk.--Wood in flint nodules.

Upper Greensand.--Foliage and cone of Sequoiites Woodwardii; cone
of Pinites oblongus.

Gault.--Cones of Pinites gracilis and P. hexagonus, Sequoiites
Gardneri and S. ovalis.

Lower Greensand.--Water-worn and bored pieces of wood; cones of
Pinites Benstedi, P. Sussexiensis, and P. Leckenbyi.

Wealden.--Driftwood, foliage of Abietites Linkii; cones of
Pinites Dunkeri, P. Mantellii, P. patens, and P. Fittoni, and
of Araucaria Pippingfordensis; foliage (and drupes?) of Thuites
Kurrianus.

Purbeck.--Fossil forest _in situ_ at Isle of Portland; cone
"nearly related to Araucaria excelsa" in the Dirt-bed.

Portland Stone.--Driftwood Araucarites.

Kimmeridge Clay.--Cone of Pinites depressus.

Oxford Clay.--Driftwood and foliage of Araucarites.

Great Oolite.--Driftwood of Araucarites; foliage of Thuites
acutifolius, T. articulatus, T. cupressiformis, T. divaricatus,
and T. expansus, and of Taxites podocarpoides; detached cones at
Helmsdale, Sutherland.

Inferior Oolite.--Wood of Peuce Eggensis (Tertiary according to
Geikie); foliage of Brachyphyllum mammillare, Cryptomerites?
divaricatus, and Palissya? Williamsonis; cones of Araucarites
sphærocarpus, A. Brodiei, and A. Phillipsii. Pinites primæva
(Lindl. and Hutt.) is a Cycadean fruit.

Lias.--Wood of Pinites Huttonianus and P. Lindleyanus; foliage
of Araucaria peregrina and Cupressus latifolia; cone of Pinites
elongatus, and "cone with long bracts like those of Pinus
bracteata," from Cromarty.

Carruthers gives the following arrangement of fossil Cycadaceæ in the Transactions of the Linn. Soc. vol. xxvi.--Firstly, the Cycadeæ: including the genus Bucklandia, Presl; and species B. anomala, B. Mantellii, B. squamosa, B. Milleriana--the two first-named species being from the Wealden, and the two last-named from the Oolite. Secondly, the Zamieæ: including the genus Yatesia, Carr.; and species Y. Morrisi, Lower Cretaceous; Y. gracilis, Lias; Y. crassa, M. Oolite; Y. Joassiana, M. Oolite; the genus Fittonia, Carr., and species F. squamata, U. Cretaceous; the genus Crossozamia, Pomel, and species C. Moreaui, Pomel, Jurassic, and C. Buvignieri, Pomel, Jurassic--both from St. Michel, France. Thirdly, the Williamsonieæ: including the genus Williamsonia, Carr.; and species W. gigas, W. pecten, W. hastula, all from the inferior Oolite. Fourthly, the Bennettiteæ: including the genus Bennettites, Carr., and species B. Saxbyanus, Wealden; B. Gibsonianus, Lr. Greensand; B. maximus, Wealden; B. Portlandicus, Lr. Purbeck; and B. Peachianus, M. Oolite; the genus Mantellia, Brong., and species M. nidiformis, M. intermedia, M. microphylla, from the Lr. Purbeck; and M. inclusa, from the Lr. Cretaceous; the genus Raumeria, Goeppert, and species R. Reichenbachiana, from Galicia, and R. Schulziana from Silesia.

FOSSIL FLORA OF THE TERTIARY OR CAINOZOIC PERIOD,

(INCLUDING THE CRETACEOUS EPOCH).

REIGN OF ANGIOSPERMS.

This reign is characterised by the appearance of Angiospermous Dicotyledons, plants which constitute more than three-fourths of the species of the existing flowering plants of the globe, and which appear to have acquired the predominance from the commencement of the Tertiary epoch. They are plants with seeds contained in seed-vessels, and each seed with two cotyledons. These plants, however, appear even at the beginning of the Cretaceous period. In this reign, therefore, Brongniart includes the upper Secondary period, or the Cretaceous system, and all the Tertiary period. The Cretaceous may be considered as a sort of transition period between the reign of Gymnosperms and Angiosperms.

_FLORA OF THE CHALK._

The Chalk flora is characterised by the Gymnospermous almost equalling the Angiospermous Dicotyledons, and by the existence of a considerable number of Cycadaceæ, which do not appear in the Tertiary period. The genus Credneria is one of the characteristic forms. In this period we find Algæ represented by Cystoseirites, Confervites, Sargassites, and Chondrites; Ferns by peculiar species of Pecopteris and Protopteris; Naiadaceæ by Zosterites; Palms, by Flabellaria and Palmacites; Cycadaceæ by Cycadites, Zamites, Microzamia, Fittonia, and Bennettites; Coniferæ, by Brachyphyllum, Widdringtonites, Cryptomeria, Abietites, Pinites, Cunninghamites, Dammarites, Araucarites; and Angiospermous Dicotyledons, by Comptonites, Alnites, Carpinites, Salicites, Acerites, Juglandites, and Credneria. At the base of the Tertiary period there are deposits of Algæ of a very peculiar form, belonging to the genera Chondrites and Munsteria. No land plants have been found mingled with these marine species.

[Sidenote: Fig. 91. _Sequoiites ovalis._ Large cone.]

In the Gault, near Folkestone, an interesting association of coniferous fruits has been found, consisting of two species of Sequoia, along with two of Pinus. The pines belong to the same group as those which now grow with the Wellingtonias in California, showing the remarkable fact that the coniferous vegetation of the high lands of the Upper Cretaceous period had a _facies_ similar to that now existing in the mountains on the west of North America. We figure both the species of Sequoiites--viz. S. ovalis (Fig. 91), a large cone, and S. Gardneri (Plate II. Fig. 7). In the present day there are two species of the genus Sequoia--viz. S. gigantea (Wellingtonia gigantea) and S. sempervirens.[20] In the Lower Greensand a remarkably fine cone belonging to the same group as the Cedar has been found. This is the Pinites Leckenbyi (Plate II. Fig. 4). A section exhibits the seeds in their true position, some of which are preserved so as to exhibit the form and position of the embryo.

[Sidenote: Fig. 92. _Pinites ovatus_ (_Zamia ovata_ of Lindley and Hutton), an ovate cone with a truncated base and obtuse apex, nearly allied to the stone-pine.]

The Tertiary period is characterised by the abundance of Angiospermous Dicotyledons and of Monocotyledons, more especially of Palms. By this it is distinguished from the more ancient periods. Angiosperms at this period greatly exceed Gymnosperms. Cycadaceæ are very rare, if not completely wanting, in the European Tertiary strata, and the Coniferæ belong to genera of the temperate regions. In the lower Tertiaries Carruthers has found a fossil Osmunda, and the existence of a group of Pines having cones with a very thick apophysis. From their remarkable external aspect, these cones had been considered to be Cycadean, but their internal structure indicates that they are coniferous. Pinites ovatus is one of these cones (Fig. 92). The Cupressineæ are found in the Tertiary beds only. Taxodieæ are represented by Sequoiites (Plate II. Fig. 7) in the Cretaceous and Eocene strata. Peuce australis of Van Diemen's Land and P. Pritchardi of Ireland are Tertiary plants. The Peuce of Eigg (P. Eggensis), according to Geikie, is also Tertiary, and not Oolitic. Isoetes is mentioned by Schimper as a Tertiary genus. Although the vegetation throughout the whole of the Tertiary period presents pretty uniform characters, still there are notable differences in the generic and specific forms, and in the predominance of certain orders at different epochs. Brongniart does not entirely agree with Unger as to these epochs. Many of the formations classified by Unger in the Miocene division he refers with Raulin to the Pliocene. He divides the Tertiary period, as regards plants, into the Eocene, Miocene, and Pliocene epochs, and gives the following comparative results from an examination of their floras:--

+-----------------+---------------+----------------+-----------------+
| Classes and | | | |
| Sub-Classes. | Eocene Epoch. | Miocene Epoch. | Pliocene Epoch. |
+-----------------+---------------+----------------+-----------------+
| Thallogenæ | 16 | 6 | 6 |
| Acrogenæ | 17 | 4 | 7 |
| Monocotyledones | 33 | 26 | 4 |
| Dicotyledones-- | | | |
| Gymnospermæ | 40 | 19 | 31 |
| Angiospermæ | 103 | 78 | 164 |
+-----------------+---------------+----------------+-----------------+
| | 209 | 133 | 212 |
+-----------------+---------------+----------------+-----------------+

_FLORA OF THE EOCENE EPOCH._

In the Eocene formation the fossil fruits of the Isle of Sheppey increase the number of Phanerogamous plants, only a small proportion of which have as yet been described. This is an exceptional locality, and the deposit in which the fruits occur is probably the silt found at the mouth of a large river which flowed, like the Nile, from tropical regions towards the north. The number of plants as given by Brongniart is much smaller than that mentioned by Unger (p. 23). The latter includes in his enumeration a considerable amount of uncertain species.

[Sidenote: Fig. 93. _Palmacites Lamanonis_. Fan-shaped (flabellate) leaf of a Palm.]

The Eocene epoch in general is characterised by the predominance of Algæ and marine Naiadaceæ, such as Caulinites and Zosterites; by numerous Coniferæ, the greater part resembling existing genera among the Cupressineæ, and appearing in the form of Juniperites, Thuites, Cupressinites (Plate II. Figs. 8, 9), Callitrites, Frenelites, and Solenostrobus; by the existence of a number of extra-European forms, especially of fruits, such as Nipadites, Leguminosites, Cucumites, and Hightea; and by the presence of some large species of Palm belonging to the genera Flabellaria and Palmacites (Fig. 93).

[Sidenote: Fig. 94. _Osmunda regalis_, Royal Fern, having a bipinnate frond and fructification in a spike-like form, the branches bearing sporangia.]

Unger says that the Eocene flora has resembled in many respects that of the present Australian vegetation. He gives the following genera as occurring at the Eocene epoch:--Araucaria, Podocarpus, Libocedrus, Callitris, Casuarina, Pterocarpus, Drepanocarpus, Centrolobium, Dalbergia, Cassia, Cæsalpinia, Bauhinia, Copaifera, Entada, Acacia, Mimosa, Inga. (Seemann's Journal of Bot. vol. iii. p. 43.) Amber is considered to be the produce of many Coniferæ of this epoch, such as Peuce succinifera or Pinites succinifera, and Pinus Rinkianus. It occurs in East Prussia in great quantity, and it is said that many pieces of fossil wood occur there, which, when moderately heated, give out a decided smell of amber. Connected with these beds are found cones belonging to Pinites sylvestrina and P. Pumilio-miocena, species nearly allied to the living species; others to Pinites Thomasianus and P. brachylepis. Goeppert contrasts the present flora of Germany and that of the Amber epoch as follows:--

German Flora. Amber Flora.

Cryptogameæ 6800 60
Phanerogameæ 3454 102

and gives the following specimens of two of the orders:--

Cupuliferæ 12 10
Ericaceæ 23 24

(See remarks by Goeppert on the Amber Flora, etc., Edin. N. Phil. Journ. lvi. 368; and Quart. Journ. Geol. Soc. x. 37.) In the lower Eocene of Herne Bay, Carruthers noticed a fern like Osmunda (Fig. 94), which he calls Osmundites Dowkeri (Plate I. Figs. 8, 9). This specimen was silicified; starch grains contained in its cells, and the mycelium of a parasitic fungus traversing some of them, were perfectly preserved. Berkeley has detected in amber fossil fungi, which he has named Penicillium curtipes, Brachycladium Thomasinum, and Streptothrix spiralis.[21] Some Characeæ are also met with, as Chara medicaginula and C. prisca, with a fossil called Gyrogonites, the nucule or the fructification of these plants. Carpolithes ovatus, a minute seed-vessel, occurs in the Eocene beds of Lewisham. Another small fruit, of a similar nature, called Folliculites minutulus, occurs in the Bovey Tracey coal, which belongs to the Tertiary beds.

_FLORA OF THE MIOCENE EPOCH._

[Sidenote: Fig. 95. _Comptonia acutiloba_, apparently the leaf of a plant belonging to the natural order Proteaceæ, which abound in Australia, and are also found at the Cape of Good Hope at the present day.]

[Sidenote: Figures 96 to 99 show the leaves of plants belonging to the Miocene epoch.]

[Sidenote: Fig. 96. _Acer trilobatum_, a three-lobed palmate leaf, like that of the Maple, with the lobes unequal, inciso-dentate, the lateral ones spreading, found at Œningen. Fig. 97. _Ulmus Bronnii_, a petiolate leaf, like that of the Elm, unequally ovato-acuminate, feather-veined and toothed, found in Bohemia. Fig. 98. _Rhamnus Aizoon_, a petiolate elliptical obtuse feather-veined leaf, with an entire margin, found in Styria.]

The most striking characters of the Miocene epoch consist in the mixture of exotic forms of warm regions with those of temperate climates. Unger says that it resembles that of the southern part of North America. Thus we meet with Palms, such as species of Flabellaria and Phœnicites, a kind of Bamboo called Bambusium sepultum; Lauraceæ, as Daphnogene and Laurus; Combretaceæ, as Getonia and Terminalia; Leguminosæ, as Phaseolites, Desmodophyllum, Dolichites, Erythrina, Bauhinia, Mimosites, and Acacia--all plants having their living representatives in warm climates; Echitonium, Plumiera, and other Apocynaceæ of equatorial regions; Comptonia (Fig. 95), a Proteaceous genus, and Steinhauera, a Cinchonaceous genus; mingled with species of Acer (Fig. 96), Ulmus (Fig. 97), Rhamnus (Fig. 98); and Amentiferous forms, such as Myrica, Betula, Alnus (Fig. 99), Quercus, Fagus, Carpinus, all belonging to temperate and cold climates. The statements as to the occurrence of Pinus sylvestris and Betula alba among the Miocene fossils have not been founded on complete data. It is by no means easy, even in the present day, to distinguish fragments of dried specimens of Pinus Pumilio from those of P. sylvestris, and from a great many other Pines. The difficulty is still greater in fossils (Hook. Kew Journ. v. 413). There are a very small number of plants belonging to orders with gamopetalous corollas. In the Miocene formation of Lough Neagh in Ireland, and of Mull in Scotland, silicified trunks of considerable size have been found. The Irish silicified wood has been denominated Cupressoxylon Pritchardi from its apparent resemblance to the Cypress. As connected with the Miocene epoch, we may notice the leaf-beds found at Ardtun, in the island of Mull, by the Duke of Argyll.[22] Above and below these beds basalt occurs, and there are peculiar tuff-beds alternating with the leafy deposits. These tuff-beds were formed by the deposit of volcanic dust in pools probably of fresh water. They contain fragments of chalk and flint. The leaves are those of plants allied to the Yew, Rhamnus, Plane, and Alder, along with the fronds of a peculiar Fern, and the stems of an Equisetum. The genera are Taxites or Taxodites (Fig. 100), Rhamnites (Fig. 101), Platanites, Alnites, Filicites, and Equisetum (Fig. 102). In the leaf-beds at Bournemouth Mr. Wanklyn detected several ferns. One is a species of Didymosorus, and shows distinct venation and fructification. Fossilised wood was found in the Arctic Regions by Captain M'Clure. At the N.W. of Banks Land he found trees with trunks 1 foot 7 inches in diameter.

[Sidenote: Fig. 99. _Alnus gracilis_, an ovate-oblong leaf, like that of the Alder, found in Bohemia.]

[Sidenote: Figures 100, 101, 102, exhibit fragments of plants which occur in the leaf-bed at Ardtun Head, in Mull, and which is referred to the Miocene epoch. The figures are from the Duke of Argyll's paper.]

[Sidenote: Fig. 100. _Taxites_, or perhaps _Taxodites Campbellii_, a branch with leaves resembling those of the Yew, or rather those of Taxodium.

Fig. 101. _Rhamnites multinervatus_, a leaf resembling that of Rhamnus.]

[Sidenote: Fig. 102. _Equisetum Campbellii_, a stem like that of an Equisetum of the present day.]

Dr. Oswald Heer[23] has examined the plants preserved in the lignite beds of Bovey Tracey, in Devonshire, and he finds that they belong to the Miocene formation. There is a remarkable coincidence between this and several of the continental fossil floras, such as those of Salzhauser in the Wetterau, Manosque in Provence, and of some parts of Switzerland. Bovey Tracey has no species in common with Iceland, although the Tertiary flora of Iceland belongs to the same period. Two of its species (Corylus MacQuarrii and Platanus aceroides) have been found in the Miocene of Ardtun Head. Even the genera are distinct, with the exception of Sequoia and Quercus. The Bovey Tracey flora has a much more southern character, corresponding entirely with that of the Lower Miocene of Switzerland. It contains three species of Cinnamon, one Laurel, evergreen Figs, one Palm, and large Ferns, thus manifesting a subtropical climate. One of the most important plants is Sequoia Couttsiæ, a Conifer which supplies a link between S. Langsdorfii and S. Sternbergi, the widely-distributed representatives of S. sempervirens and S. gigantea (Wellingtonia), which are Californian trees. Among other characteristic plants may be mentioned Cinnamomum lanceolatum and C. Scheuchzeri; Quercus Lyellii, an evergreen oak; species of evergreen fig (Ficus Falconeri and F. Pengellii), Palmacites Dæmonorops, a prickly twining Rotang-palm; species of Vine (Vitis Hookeri and V. Britannica); Pecopteris lignitum, a large tree-fern; species of Nyssa, at present confined to North America. Among other plants recorded by Heer in his paper are the following:--Laurus primigenia, Daphnogene Ungeri, species of Dryandroides, Andromeda, Vaccinium acheronticum, Echitonium cuspidatum, Gardenia Wetzleri, species of Anona, Nymphæa Doris, Carpolithes Websteri, C. Boveyanus, and other species. In the post-tertiary white clay of Bovey Tracey, Salix cinerea, and a species allied to S. repens, as well as Betula nana, are found.

The Arctic fossil flora (Miocene), according to Heer, amounts to 162 species: Cryptogamia, 18 species, of which 9 are large ferns; Phanerogamia, Coniferæ, 31; Monocotyledons, 14; Dicotyledons, 99. Among the Coniferæ are--Pinus M'Clurii, Sequoia Langsdorffii, Sternbergi, and Couttsiæ, Taxodium dubium, Glyptostrobus europæus, Thujopsis europæa. Among leafy trees are--Fagus Deucalionis, Quercus Olafseni, Platanus aceroides, willows, beeches, Acer, Otopteryx, tulip-tree, walnuts, Magnolia Inglefieldi, Prunus Scottii, Tilia Malmgreni, Corylus M'Quarrii, Alnus Kefersteinii, Daphnogene Kannii, probably one of the Lauraceæ; and among Proteaceæ, MacClintockia? and Hakea. In Greenland are found species of Rhamnus, Paliurus, Cornus, Ilex, Cratægus, Andromeda, Myrica, Ivy, and Vine. From the flora of Spitzbergen, in the Miocene epoch, we may conclude that under 79° N. lat. the mean temperature of the year may have been 41° Fahr., while at the same epoch that of Switzerland was 69°·8 Fahr.; judging from the analogy of floras, it appears that the mean temperature has fallen 6°·9. From this it follows that at Spitzbergen, at 78° N. lat., the mean temperature was perhaps 41°·9 Fahr. In Greenland, at 70°, it would be 49°·1 Fahr., and in Iceland and on the Mackenzie, in lat. 65°, it would be 52°·7 Fahr. At the Miocene epoch the temperature seems to have been much more uniform, the mean heat diminishing much more gradually in proportion as the pole was approached. The isothermal line of 32° Fahr. might have fallen upon the pole, while now it is situated under 58° N. (See Heer's conclusions as to changes of temperature depending on proportion of sea and land, eccentricity of the earth, and the earth moving through warm and cold spaces in the universe--Ann. Nat. Hist. 4th ser. i. 66.)

In speaking of the Polar flora of former epochs, Heer says that every plant executes a slow and continuous migration. These migrations, the starting-point of which is the distant past, are recorded in the rocks; and the interweaving of the carpets of flowers which adorn our present creation retraces them for us in its turn. For the vegetation of the present day is closely connected with that of preceding epochs; and throughout all these vegetable creations reigns _one_ thought, which not only reveals itself around us by thousands upon thousands of images, but strikes us everywhere in the icy regions of the extreme north. Organic nature may become impoverished there, and even disappear when a cold mantle of ice extends over the whole earth; but where the flowers die the rocks speak, and relate the marvels of creation; they tell us that even in the most distant countries, and in the remotest parts, nature was governed by the same laws and the same harmony as immediately around us.[24]

_FLORA OF THE PLIOCENE EPOCH._

The flora of the Pliocene epoch has a great analogy to that of the temperate regions of Europe, North America, and Japan. We meet with Coniferæ, Amentiferæ, Rosaceæ, Leguminosæ, Rhamnaceæ, Aceraceæ, Aquifoliaceæ, Ericaceæ, and many other orders. There is a small number of Dicotyledons with gamopetalous corollas. The twenty species with such corollas recognised by Brongniart are referred to the Hypogynous Gamopetalous group of Exogens, which in the general organisation of the flowers approach nearest to Dialypetalæ. In this flora there is the predominance of Dicotyledons in number and variety; there are few Monocotyledons. No species appear to be identical, at least with the plants which now grow in Europe. Thus the flora of Europe, even at the most recent geological epoch of the Tertiary period, was very different from the European flora of the present day.

Taking the natural orders which have at least four representatives, Raulin[25] gives the following statement as to the Tertiary flora of central Europe. The Eocene flora of Europe is composed of 128 species, of which 115 belong to Algæ, Characeæ, Pandanaceæ, Palmæ, Naiadaceæ, Malvaceæ, Sapindaceæ, Proteaceæ, Papilionaceæ, and Cupressineæ. The Miocene flora has 112 species, of which 69 belong to Algæ, Palmæ, Naiadaceæ, Apocynaceæ, Aceraceæ, Lauraceæ, Papilionaceæ, Platanaceæ, Quercineæ, Myricaceæ, and Abietineæ. The Pliocene flora has 258 species, of which 226 belong to Algæ, Fungi, Musci, Filices, Palmæ, Ericaceæ, Aquifoliaceæ, Aceraceæ, Ulmaceæ, Rhamnaceæ, Papilionaceæ, Juglandaceæ, Salicaceæ, Quercineæ, Betulaceæ, Taxaceæ, Cupressineæ, and Abietineæ. The Eocene species are included in genera which belong at the present day to inter-tropical regions, comprising in them India and the Asiatic islands of Australia. Some are peculiar to the Mediterranean region. The aquatic plants, which form almost one-third of the flora, belong to genera now peculiar to the temperate regions of Europe and of North America, or occurring everywhere. The Miocene species belong to genera, of which several are found in India, tropical America, and the other inter-tropical regions, but which for the most part inhabit the sub-tropical and temperate regions, including the United States. Some of the genera are peculiar to the temperate regions. The aquatic genera, poor in species, occur everywhere, or else solely in the temperate regions. The Pliocene species belong to genera which almost all inhabit the temperate regions, either of the old continent or of the United States. A few only are of genera existing in India, Japan, and the north of Africa. These various floras, which present successively the character of those of inter-tropical, sub-tropical, and temperate regions, seem to indicate that central Europe has, since the commencement of the Tertiary period, been subjected, during the succession of time, to the influence of these three different temperatures. It would appear, then, Raulin remarks, that the climate of Europe has during the Tertiary period gradually become more temperate.

Brown coal occurs in the upper Tertiary beds, and in it vegetable structure is easily seen under the microscope. Goeppert, on examining the brown coal deposits of northern Germany and the Rhine, finds that Coniferæ predominate in a remarkable degree; among 300 specimens of bituminous wood collected in the Silesian brown coal deposits alone, only a very few other kinds of Exogenous wood occur. This seems remarkable, inasmuch as in the clays of the brown coal formation in many other places leaves of deciduous Dicotyledonous trees have been found; and yet the stems on which we may suppose them to have grown are wanting. The leaves have been floated away from the place where they grew by a current of water which was not powerful enough to transport the stems. The coniferous plants of these brown coal deposits belong to Taxineæ and Cupressineæ chiefly; among the plants are Pinites protolarix and Taxites Ayckii. Many of the Coniferæ exhibit highly compressed, very narrow annual rings, such as occur in Coniferæ of northern latitudes. Goeppert has described a trunk, or rather the lower end of a trunk, of Pinites protolarix, discovered in 1849 in the brown coal of Laasan in Silesia. It was found in a nearly perpendicular position, and measured more than 32 feet in circumference. Sixteen vast roots ran out almost at right angles from the base of the trunk, of which about four feet stood up perfect in form, but stripped of bark. Unfortunately the interior of the stem was almost entirely filled with structureless brown coal, so that only two cross sections could be obtained from the outer parts, one sixteen inches, the other three feet six inches broad. In the first section Goeppert counted 700, in the second 1300 rings of wood, so that for the half-diameter of 5½ feet, at least 2200 rings must have existed. As there is every reason to believe that the rings were formed in earlier ages just as the annual zones are now, this tree would be from 2200 to 2500 years old. Exogenous stems in lignite are often of great size and age. In a trunk near Bonn, Nöggerath counted 792 annual rings. In the turf bogs of the Somme, at Yseux near Abbeville, a trunk of an oak-tree has been found above 14 feet in diameter.

_GENERAL CONCLUSIONS._