Chapter 11

[136]I know not a more delightful and instructive branch of science for the young and inquiring of both sexes, than this department of Fossil Botany, which the recent improvements in the microscope have rendered so accessible; and yet there are but few cultivators of fossil botany in England!

The great value of these data will be shown in the sequel.

The stems, fruit, and foliage, of Coniferæ, occur in the various fossiliferous deposits, from those containing the earliest traces of terrestrial vegetation to the newest tertiary strata; and a large proportion of the petrified wood found in the British formations belongs to trees of this order. The presence of rows of ducts on the ligneous fibres, which is peculiar to this division of gymnosperms, as we have already explained (ante,p. 58.), is so easily detected by microscopic examination, that the merest fragment of fossil coniferous wood retaining internal structure, may without difficulty be recognized. The number of rows, and the opposite or alternate arrangement of the areolæ, are characters which, in the living pines and firs, enable us to refer the respective trees to European or exotic forms; but in the fossil coniferous wood, much diversity exists in other not less important points of structure, and for the successful cultivation of this department of fossil botany, works especially devoted to the subject must be consulted. To the English student, Mr. Witham's beautiful volume, "Observations on the Structure of Fossil Vegetables, Edinburgh, 1831," will be found a valuable guide.

FOSSIL CONIFEROUS WOOD.

Fossil Coniferous Wood.—The coniferous wood of the secondary formations of England, belongs for the most part to the Araucarian type: that is, the glands, when in double rows, are placed alternately, as in the Norfolk Island Pines (Wond.p. 696), and not side by side, as in the common European species of firs and pines (Bd.p. 486). Numerous sections of this kind of fossil wood are figured by Mr. Witham, from specimens obtained from Lennel Braes, on the banks of the Tweed, near Coldstream; and from near Allanbank Mill, in Berwickshire (Obs. Foss. Veg.p. 14); a fossil trunk, 40 feet long, discovered in Craigleith Quarry, near Edinburgh, at a depth of 136 feet, possessed the same structure.

Palæoxylon(coniferous wood of the Coal Measures).—The existence of coniferous trees in the Carboniferous flora, and the fact that their trunks and branches had contributed to the formation of coal, was first discovered and clearly demonstrated by Mr. Witham in the work to which reference has been made. Figures of the peculiar structure observable in thin slices of coal, are given inObs. Foss. Veg.pl. iii. iv. v. This carbonized wood resembles that of the Araucariæ in the multiple series of ducts, and their alternate arrangement; but the presence of thick compound medullary rays in these stems,—a character unknown in any living conifers,—led M. Brongniart to place them in a separate genus—Palæoxylon(ancient wood); characterized by the presence of medullary rays formed of numerous layers of cells, which are not arranged in superimposed series, and that present a lanceolate or oval form, in a section perpendicular to their direction.[137]

[137]ThePinites Withami, andP. medullaris, of Lindley and Hutton, figured in Mr. Witham's work, belong to this genus. It may interest the reader to know that slices of these woods prepared for the microscope by Mr. Nicol, (presented to me by the late Dr. Henry, of Manchester,) not only expose the vegetable organization in an admirable manner, but also form beautiful objects for the exhibition of polarization.

Peuce.—Another species of coniferous wood from the coal is thus named; it differs from the former in the medullary rays being composed but of one layer of superposed cells.

Araucarites(Dadoxylon of Endlechen).—This term is employed to designate the fossil wood whose structure is apparently identical with that of the living species of Araucariæ, having the same kind of medullary rays, and the ligneous fibres studded with discs or areolæ, which are polygonal, often hexagonal, and disposed in several alternating series. This wood is common in the Lias, Oolite, Wealden, and Chalk.

Drifted fragments of coniferous wood of this type occur in the Stonesfield slate, associated with leaves and fruits of cycadeæ, and with marine shells, bones of reptiles, fishes, and mammalia; at Scarborough, with the ferns and zamiæ previously described; at Swindon, in the Portland oolite, with belemnites, ammonites, trigoniæ, &c.

STERNBERGIA.

Sternbergia.—To the Araucarian tribe, according to the recent investigations of Professor Williamson, must be referred certain fossil stems found in the coal-measures, and namedSternbergiæ.[138]These are long solid cylindrical casts of sandstone or clay, with annular constrictions, which are generally invested with a thin film of carbonaceous matter; when this crust is removed the surface is found to be marked with longitudinal ridges. These fossils were once supposed to be the stems of plants allied to Yucca or Dracæna; but, as was first shown by Mr. Dawson and Mr. Dawes,[139]they are merely sandstone casts of the medullary axis or cylinder of an extinct genus of coniferæ, allied to the Araucariæ: a specimen in which the cast wassurrounded by a thick ligneous cylinder, heaving enabled that acute observer to detect the structure of the original.[140]The Sternbergiæ are sandstone casts of central cavities existing within the true pith; which cavities, under some favourable conditions, were filled with inorganic materials. Mr. Williamson is inclined to believe that all the coniferous wood from the coal-measures, belonging to the genusDadoxylon, is referable to the trees of whose piths theSternbergiæ approximatæare internal casts; and that some of the foliaceous appendages of these trees have been confounded with Lepidodendra.[141]

[138]See Pictorial Atlas, pl. xviii. p. 53.[139]On the Coal formation of Nova Scotia, Geol. Proc. 1846.[140]See Prof. Williamson's Memoir on Sternbergia, Manchester Philos. Trans. 1851.[141]Ibid. p. 355.

[138]See Pictorial Atlas, pl. xviii. p. 53.

[139]On the Coal formation of Nova Scotia, Geol. Proc. 1846.

[140]See Prof. Williamson's Memoir on Sternbergia, Manchester Philos. Trans. 1851.

[141]Ibid. p. 355.

Petrified Forests of Conifers.—The most remarkable assemblage of fossil conifers is that presented in the well-known quarries in the Island of Portland, to which allusion was made when describing the Mantelliæ obtained from that locality (ante,p. 157.). Referring toWond.p. 385,[142]for an account of the geological circumstances under which the phenomena occur, it will suffice to state that a forest of pines appears to have been submerged, and the trunks to have become petrified, whilst standing erect on the spot where they grew; the Cycads still shoot up as it were between the stems, and the roots of the trees, though changed into flint, extend into the bed of mould whence they originally derived support, and which is so little altered in appearance, as to be called theDirt-bed, by the quarrymen; thus realizing the fable of the petrified city in Arabian story, whose inhabitants were turned into stone, in the varied attitudes of life.

[142]Geol. I. of Wight, p. 394. Petrifactions, p. 56.

No foliage has been observed in connexion with these trees; not a leaf has been found in the rocks: a cone,nearly related to the fruit of Araucaria excelsa, was discovered in the Dirt-bed.

At Brook-point, in the Isle of Wight, an equally interesting fact may be observed. At the base of the cliff, which is entirely composed of Wealden clays, shales, and sandstones, there is a vast accumulation of petrified firs and pines, imbedded in the indurated grit that forms the lowermost strata on the sea-shore, and of which the reefs and rocks, produced by the encroachments of the sea, and that extend far from land, are composed. These can be examined at low-water, and the observer, upon lifting up the fuci and algæ which cover them, will find the rocks and masses of stone to consist of petrified trunks of coniferæ. There are no erect trees as in Portland; on the contrary, the stems are prostrate, and lie confusedly intermingled, and associated with bones of Iguanodons and other reptiles, and large mussel-shells; the whole presenting the characters of a raft of forest trees which had drifted down the stream of a vast river, and entangled in its course the limbs and carcasses of animals that were floating in the water, and the shells that inhabited the river, and at length became submerged in the bed of the delta or estuary. Both foliage and fruit have been found in the Wealden deposits at Brook, and will be described hereafter.[143]

[143]See Geol. I. of Wight, chap. x. and xi.

In the sands of the Desert of Sahara, in Egypt,—among the mammalian bones of the Sub-Himalayas,—and in the tertiary deposits of Virginia associated with cycads,—drifted trunks of conifers have been discovered.

Fossil trees of this family also occur in various localities in Australia and Van Diemen's Land, the wood of which is in some parts calcified, and in others silicified. The same trunk often has externally a white friable calcareous zone, several inches thick, traversed by veins of silex, or opaline chalcedony, while the centre is a silicified mass; inboth states the internal structure may be detected. This kind of fossil wood is to be seen in most cabinets, a large quantity having been sent to England by emigrants.[144]These fossil trees appear to have been subjected to the same mutations as those of the Isle of Portland, for they 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 branches being scattered around them. They so entirely preserve their natural appearance, that one of the colonists mentions among the extraordinary sights he witnessed on his first arrival in New Holland, the burning of trees into lime to manure the ground.

[144]My late friend, Sir Francis Chantrey, had a magnificent specimen, which, is now in the British Museum. See Petrifactions, p, 59.

FOSSIL CONIFERÆ OF AUSTRALIA.

A fossil pine forest, on the eastern coast of Australia, in the inlet called Lake Macquarrie, is described by the Rev. B. Clarke, as occurring at the base of a mountain range, composed of conglomerate and sandstone, with subordinate beds of lignite; an alluvial plain extends to the water's edge, covering the sandstone rock which is seenin situbeneath. Throughout this plain, stumps of fossil trees project from the ground, and present the appearance of a forest in which the trees have all been broken off at 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 out of the water. Many of the fossil stems on the strand have the remains of roots extending into the sandstone below the alluvial deposit, and, like those in the Island of Portland, are in some instances surrounded by an accumulation of rock, which forms a mound of a higher level than the surface of the stratum. The trunks are, generally, three or four feet high, and from two to six feet in diameter. The wood is silicified, and veins of chalcedony traverse its substance between the concentric rings and medullary rays; in several examples, from 60 to 120 annual circles of growthwere observable. Beds of lignite occur in the neighbouring hills, both above and below the fossil trees; many localities along the eastern coast of Australia are mentioned, as presenting similar phenomena. I may add that the only fragment of petrified wood found by Mr. Walter Mantell in New Zealand is coniferous.

In the valley of the Derwent, in Australia, opalized coniferous trees of a similar character were observed under very extraordinary circumstances, by the distinguished traveller, Count Strzelecki. Truncated stems were found standing erect in a bed of scoriaceous basalt (lava) and trachytic conglomerate: but in some instances only basaltic casts of the trunks remain. This curious phenomenon can only be explained by supposing the silicified stems to have resisted the intense heat of the incandescent lava, while trees placed in circumstances unfavourable to their petrifaction were consumed: but the latter, being either saturated with water, or fresh and green, were burnt slowly, and left cylindrical moulds in the cooled basaltic scoriæ, with impressions of the external surface of the bark; these moulds were filled Tip by a subsequent eruption, and thus basaltic casts of the consumed trees were formed.[145]

[145]Physical Description of New South Wales, by Count Strzelecki.

Coniferous Wood in Oxford Clay.—It would occupy too much space to notice the numerous localities in which fossil remains of conifers occur in the Liassic and Oolitic formations of England.

In the Oxford and Kimmeridge Clays water-worn trunks and branches of large pine-trees are often met with. An interesting deposit of these remains was brought to light by my youngest son (Mr. Reginald Mantell), when constructing the branch line of railway from the Great Western to Trowbridge, in Wilts. In the progress of the work, extensive sections were cut through the Oxford Clay, and laid bare a large quantity of drifted wood, much of which was notpetrified, but in the state of bog-wood, and was used for fuel by the workmen. Trunks ten or twelve feet long were met with, to which serpulæ, oysters (Ostrea delta), and other shells were adherent. These vegetable remains were associated with Belemnites, Belemnoteuthides, Ammonites, &c.; and had evidently been drifted far out to sea by currents.[146]

[146]SeeWond.p. 502. Geol. Journal, vol. vi. p. 311.

FOSSIL CONIFEROUS WOOD.

Coniferous Wood in the Chalk formation.—The arenaceous limestones of the Greensand of Kent and Sussex abound, in some localities, in water-worn masses of coniferous wood, which are often perforated by boring mollusks, asTeredo,Fistulana,Gastrochæna, &c. In the Iguanodon quarry of Kentish rag, near Maidstone, large quantities of these remains occur, and Mr. Bensted has collected several cones belonging to different kinds of conifers; one of these appears to be a species ofAbies, or Fir:[147]it was associated with fragments of trunks and branches, whose internal structure proved their relation to the fruit.Plate V. fig. 2, are microscopic views of transverse and longitudinal sections of this wood; 2ashows the cellular tissue in a transverse slice, seen by reflected light; 2ba vertical section in the direction of the medullary rays, exhibiting the vessels studded with single rows of glands. This wood occurs both in a calcareous and siliceous state; in some examples the external zones are calcareous, and the inner siliceous; in others the entire branch is changed into black flint, in which the coniferous structure is beautifully preserved.

[147]It is figured and described asAbies Benstedi, by the Author. Geol. Proc. January, 1843.

Near Willingdon, in Sussex (Geol. S. E.p. 172), a bed of sand, immediately beneath the Galt, contains a layer of water-worn fragments of stems and branches, of small size; they are generally perforated byGastrochænce, and the cavities formed by these depredators are filled with particles of green chlorite sand. The structure of this wood is representedinPlate V. fig. 3aa transverse, and 3ba vertical section, viewed by reflected light; in 3bthe vessels are dotted with two parallel longitudinal rows of very minute glands, arranged alternately, as in the Araucariæ; a fragment of one of the medullary rays is seen near the middle of the specimen.

In this deposit of coniferous wood, two or more fruits apparently referable toZamiæhave been discovered; one specimen, five and a half inches long, and of an elongated cylindrical form, covered with rhomboidal eminences, I have figured and described asZamites Sussexiensis.[148]

[148]Geol. Proc. 1843.

Lign. 58. Fragment of Coniferous Wood in Flint.From a wall in Lewes Priory,

The White Chalk of England has afforded but few traces of plants of this family. Fragments of coniferous wood are, however, occasionally found in the state of carbonaceous, or reddish brown friable masses, and when this substance is removed, the surface of the chalk is seen to be marked with impressions of ligneous fibres; sometimes the surface isstudded over with little pyriform eminences, which are cretaceous casts of perforations made by insects in the wood. These specimens, when all traces of the wood are absent, are very puzzling to those who are not aware of their origin.

Occasionally silicified fragments of wood are found imbedded in flint. I have an interesting specimen of this kind obtained from a wall in Lewes Priory (Lign. 58), and though it must have been exposed to the influence of the weather for nearly eight centuries, its surface still exhibits coniferous structure.

WOOD IN FLINT.

Tertiary Coniferous Wood.—The Tertiary formations in some localities abound in coniferous plants and trees, which, in the Paris basin, are associated with bones of mammalia; several species of pine (Pinus) and of yew (Taxus) from those deposits are described by M. Brongniart. I have collected fossils of this kind from the London Clay of the Isle of Sheppey, Bracklesham Bay, and Bognor in Sussex, and Alum Bay, in the Isle of Wight; and from the plastic clay at Newhaven.

Fossil Foliage and Fruit of Conifers.—From this digression on the pine-forests and drift-wood of the secondary formations, we return to the examination of the foliage and fruits of this order of vegetables that are preserved in the mineral kingdom.

Araucaria peregrina(Lindley and Hutton).Lign. 59, fig. 1.—With the trunks and branches of conifers of the Lias, cones and foliage are occasionally found: a beautiful example of a branch with the leaves preserved, is figured,Lign.59. This fossil has been so admirably cleared from the shale which invested it (by Miss Philpot) that even the surface of the leaves is exposed. It so closely resembles a twig ofAltingia excelsa, that the eminent authors of Foss. Flor. have named it as above. But M. Brongniart states that the foliage differs from that of the two living groups of Araucariæ: inAraucaria Brasiliensis, the leavesare flat, inAltingia excelsa, quadrangular; in the fossil the leaves are short, fleshy, arranged spirally, and inserted.

Lign. 59.Fig.1.—Part of a Branch of Araucaria peregrina;nat.Lias, Lyme Regis.2.—Calamites nodosuswith foliage;nat.Coal-shale, (seeante,p. 109.).

Pinites; a name applied to those fossil leaves and fruits which agree in their general character with the recent genus Pinus; upwards of thirty species are known.[149]In the Pines, as botanically distinguished from the Firs (Abies), the leavesarise in bundles of from two to five; and the scales of the cones are thickened, and terminate in discs more or less defined. In Firs, (Larch, Cedar, &c.) the scales have thin edges, and the leaves are solitary.

[149]See Endlechen's Synopsis Coniferarum.

Pinites Fittoni.Geol. Isle of Wight; 2d edit, p. 457.—Several cones with the above characters have been found in the Wealden formation. A cone figured and described by Dr Fitton, is remarkable for a double prominence on each scale: It was supposed to resemble the fruit ofDammara, but the strobilus of the latter is like that of the Cedar of Lebanon, in which the edges of the scales are thin. The Wealden fossil appears to be a genuine pine, and may be distinguished by the name of its discoverer,Pinites Fittoni; a small figure of the only known specimen is given,Wond.p. 399,fig.4.

I have collected from the Wealden strata of the Isle of Wight three or four small cones, which resemble those of a species of Araucaria; they are ovate, imbricated, with acuminated scales, which are recurved at the apex. The fossils figured inWond.p. 399,figs.2 and 3, are, I believe, water-worn specimens of the same species.[150]

[150]I subjoin a definition of the genera Pinus and Abies, for the use of the student.Pinus.—Fruit-catkins ovate, roundish, or cylindrical closely set with thick two-flowered scales; forming an imbricated cone, composed of numerous ligneous angular, or flat, rigid scales, having attached to the inside of each two seeds crowned with a thin membraneous, falcate, oblong, or roundish wing; the scales are composed of a thick woody substance, forming an angular surface, with a recurved point. The Pines are evergreen trees, with from two to five narrow, angular leaves springing from each sheath. Cotyledons four to twelve.Abies.—Cones with thin flat scales, which are more membranous at the extremities than in Pines: the leaves are emarginate, short solitary, needle-shaped, angular or flat.

[150]I subjoin a definition of the genera Pinus and Abies, for the use of the student.

Pinus.—Fruit-catkins ovate, roundish, or cylindrical closely set with thick two-flowered scales; forming an imbricated cone, composed of numerous ligneous angular, or flat, rigid scales, having attached to the inside of each two seeds crowned with a thin membraneous, falcate, oblong, or roundish wing; the scales are composed of a thick woody substance, forming an angular surface, with a recurved point. The Pines are evergreen trees, with from two to five narrow, angular leaves springing from each sheath. Cotyledons four to twelve.

Abies.—Cones with thin flat scales, which are more membranous at the extremities than in Pines: the leaves are emarginate, short solitary, needle-shaped, angular or flat.

WALCHIA.

Walchia.Lign. 60.—The fossil coniferæ thus named by Sternberg, have numerous closely set, regularly pinnatedbranches, resembling those ofAraucaria excelsa, and which are thickly beset with foliage. The leaves are sessile, compact, enlarged at the base, tetragonal or falciform, and slightly decurrent; they often vary considerably in form and length on the same bough. The branches are in some examples terminated by oblong cones, composed of imbricated, oval or lanceolate, pointed scales, the summits of which are not recurved, as in the Araucariæ. The trees of this genus are closely related to theAraucaria excelsa, andA. Cunninghami. Some species occur in the Coal formation at St. Etienne and Autun;[151]others (asWalchia hypnoides) in the schists of Lodève, and in the copper slates of the Zechstein in Mansfeld.[152]

[151]"Mines de Houille de Vettin, &c." See "Tableau des Vég. Foss." p. 70, par M. Brongniart.[152]Missing!

[151]"Mines de Houille de Vettin, &c." See "Tableau des Vég. Foss." p. 70, par M. Brongniart.

[152]Missing!

Lign. 60. Walchia hypnoides;1/3nat.Permian, Lodève.Part of a bough with six of the branches bearing terminal cones.

Abietites.—To the Abies, or Fir, several cones found in the Wealden deposits of Sussex and Hants closely approximate in the form and structure of their scales. The most remarkable is the very elongated coniferous fruit, first discovered by me in the Wealden at Brook Point, and described and figured in my Geology of the Isle of Wight (2d edit.p. 452), under the name ofAbietites Dunkeri, in honour ofthe eminent geologist who has so successfully and diligently explored the Wealden of the North of Germany.

I have been so fortunate as to collect from thirty to forty specimens of these fruits of the conifers of the country of the Iguanodon, associated with trunks and branches, and imperfect vestiges of single lanceolate leaves.

Lign. 61.Abietites Dunkeri.Wealden; Isle of Wight;1/3nat.Fir-cone, showing the imbricated scales, and many bracteæ.

ABIETITES DUNKERI.

Abietites Dunkeri.Lign. 61.—These cones are of a cylindrical form, and greatly elongated: the largest specimen is thirteen inches in length, and but three inches in circumference. The scales are broad, slightly convex without and concave within, obovate or subrotund, with a prominent midrib, edges thin and entire. Leaves solitary, slender, slightly curved, from 1 inch to 11/2inch in length. The cones were garnished with bracteæ, which are seen on the margins of the fossil when imbedded in the rock. Whether the foliage that forms the constituent substance of a large proportion of the bituminous coal of Hanover (ante,p. 74.), and which has been figured and of the named by Dr. DunkerAbietites Linkii, belongs to the same species of Fir as these cones, I am unable to determine. The seeds are of an ovate form: the pericarp is in the state of carbon, and filled or lined with pyrites or calc-spar.

These cones are generally found more or less pyritified, and are extremely beautiful objects when first collected; but like the fruits from the Isle of Sheppey, similarly mineralized, often decompose, in spite of every precaution, after exposure to the air but for a few weeks.

A small sub-ovate fir-cone found with coniferous wood inthe Kentish-rag of Mr. Bensted's quarry, near Maidstone, (ante,p. 173.), and figured and described by me asAbies Benstedi, probably belongs to the coniferæ of the Wealden, since it was associated with drifted bones of the Iguanodon.

Fossil Cypresses.—The tribe of conifers calledCupressusor Cypress, (distinguished from the firs and pines by the leaves being mere scales, and the cones consisting of small wooded peltate bracteæ, and by other botanical characters,) including the Juniper and Arbor-vitæ, appears to have flourished during the whole of the secondary epochs; for fossil leaves and stems referable to this family, but whose generic affinities cannot be determined with precision, have been found in the Trias, Lias, Oolite, and Wealden deposits.

Lign. 62.Thuites Kurrianusnat.Wealden. Hastings.

Thuites Kurrianus.Lign. 62.—TheThujaor Arbor-vitæ, a plant too well known to require description, is the type of the fossil plants distinguished by the name ofThuites. Many years since I discovered vestiges of branches and leaves of some species of this genus, in the ironstone of the Wealden beds, at Heathfield in Sussex (Geol. S. E.p. 228); and of late, many specimens have been found in strata of the same formation in England and Germany. The branch here figured, from the cabinet of S. H. Beckles, Esq. will serve to illustrate the appearance of these fossil plants. Some small fruits found in the ironstone of Heathfield may possibly belong to Cypresses. The foliage and fruit of five or six distinct species of Thuites have been discovered in Tertiary strata.

Voltzia.[153](Wond.p. 547).—This extinct genus of plantsis peculiar to the Trias (Grès bigarré) or New Red deposits, and is one of the most characteristic of the fossil coniferæ. The specimens first found were fromSultz-les-Bains, near Strasburgh. The leaves are alternate, arranged spirally, sessile, and decurrent, and have much analogy with those of certain Araucariæ. The fruits are oblong cones, with cuneiform scales, slightly imbricated, not contiguous, and generally with from three to five lobes.

[153]Named in honour of the late M. Voltz, of Strasburgh, by whom they were first discovered. The specimens in the British Museum, from my collection, were presented to me by M. Voltz.

TAXITES. NŒGGERATHIA. FOSSIL RESINS.

Taxites.—Some branches found in the Stonesfield slate, and bearing a general resemblance to twigs of Yew (Taxus), are described under the above name, but their analogies are doubtful. (Seeante,p. 145.)

Nœggerathia.[154]—I must briefly notice the coal-plants which M. Brongniart has placed under this genus, because the foliage of some species appears to have entered largely into the formation of certain seams of coal, although the perfect form of the leaves is unknown. The foliage referred to Nœggerathia consist of pinnated, or deeply pinnatifid, simple leaves. These leaves, or leaflets, are either elongated, linear, lanceolate, wedge-shaped or flabelliform, and entire, or deeply lobed at their extremity, and are traversed by numerous, fine, equal nerves, slightly diverging from the base, but almost parallel. The affinities of these plants are not satisfactorily made out: M. Brongniart considers them to approach nearest to the Cycads or Conifers; perhaps forming a connecting tribe between those two great groups of gymnosperms.[155]

[154]A leaf ofN. flabellatais figured in Foss. Flor.[155]Tab. Veg. Foss. p. 64.

[154]A leaf ofN. flabellatais figured in Foss. Flor.

[155]Tab. Veg. Foss. p. 64.

Fossil Resins.—Amber.—The resinous secretions of Conifers are occasionally found in a fossil state. When the tunnel was carried through Highgate Hill, in 1811, concretionary lumps of a brittle substance were discovered, which proved, upon analysis, to be the resin of a coniferous treechanged by mineralization. In a bed of fossil wood, near Hythe, in Kent, a resin was found that partook of the properties of amber and retinasphalt; it was of a clear red colour, very infusible, and acted upon with difficulty by many chemical solvents.[156]

[156]Geological Proceedings, 1843.

The pollen of pines or firs occurs in a tertiary deposit at Egra, in Bohemia; this bed is entirely composed of pollen and the frustules of many kinds of diatomaceæ.[157]

[157]Described by M. Ehrenberg.

AMBER. FOSSIL PALMS.

Amber, so remarkable for its electrical properties, and so largely used for ornamental purposes, is a fossil resin, the product of an extinct species of pine (Pinus succinifer), which, though nearly allied toPinus abies, andP. picea, is essentially distinct. The Amber in the European markets is principally collected from the shores of the Baltic, between Memel and Konigsberg, being washed out of submerged beds of lignite, and thrown up on the strand by the waves. Amber is occasionally found on the eastern and northern shores of England. The forests of Amber-pines appear to have been situated in the south-eastern part of what is now the bed of the Baltic, in about 55° north latitude, and 37° to 38° east longitude, and were probably destroyed at the commencement of the Drift period.

Insects, spiders, small crustaceans, leaves, and fragments of vegetable tissue, are often imbedded in amber; and a few hairs and feathers of mammalia and birds have been detected. These organic bodies must have become immersed in this substance when it exuded from the trees in a viscid state, for they are often preserved as fresh and beautiful as if recently embalmed in the liquid resin. Upwards of 800 species of insects have been discovered, chiefly referable to Aptera, Diptera, Neuroptera, Coleoptera, Libellula, &c.: by far the greater number belong to extinct forms.

The vegetable remains comprise four species of pine, andspecies of cedar, cypress, juniper, yew; and of oak, poplar, beech, ash, &c.; and a few ferns, mosses, liverworts, confervæ, and fungi. The Amber appears to have exuded from the bark and wood, but chiefly from the root-stock, as is the case with theCopalandAnimé, which are resinous substances obtained from certain trees in India and America, and largely employed for varnish: these resins are often substituted for true amber, especially when they contain insects, &c.; but the latter are always of the existing indigenous species of the country. The difference observable in the colour of the various species of amber, is attributable to accidental chemical admixtures.[158]

[158]Petrifactions, p. 23.

Fossil Palms(Palmacites).—Reserving an account of the fossil plants belonging to the other grand division of Dicotyledons, theAngiosperms(ante,p. 61.), for the last section of the present chapter, I proceed to notice the most important family of theEndogens, orMonocotyledons, whose remains occur abundantly in many tertiary deposits—thePalms.

The Palms are, for the most part, lofty trees, having a single cylindrical stem, which, like that of the arborescent ferns, rises to a great height, and is crowned with a canopy of foliage. The trunks are solid, most dense on the outer part, and in some species (as the Cane-palms) are coated with a thin siliceous epidermis. At a little distance above the surface of the ground, strong, simple, rope-like roots are sent off from the stem, appearing like clusters of stays or braces to support the trunk; and the base of the petrified palm-trees often exhibits vestiges of these organs.[159]The leaves are supported by petioles, and are in most species very large;[160]they are either pinnated or flabellated (fan-shaped), and sometimes nearly split in half: the veins or nervuresare parallel, and the interspaces plaited like the folds of a fan. The surface of the stem is scored by transverse scars formed by the separation of the petioles, and these markings assist in the identification of the fossil trunks of palm-trees. The fruit is in some kinds a single drupe, as the Cocoa-nut; in others a cluster of soft pericarps, as the Date.

[159]Specimens in the Brit. Mus. Petrifactions, p. 12.[160]In the Fan-palm (Corypha), the leaf is sometimes twenty feet broad.

[159]Specimens in the Brit. Mus. Petrifactions, p. 12.

[160]In the Fan-palm (Corypha), the leaf is sometimes twenty feet broad.

The Palm family is divided into upwards of sixty genera, comprising more than a thousand species: the greater number are inhabitants of tropical countries. Stems, with the external surface and internal structure preserved, and the foliage, and fruit, of several kinds of Palms, have been found in a fossil state, and chiefly in the Tertiary formations. Examples of the large silicified palm-stems from the West India Islands, where they occur imbedded with corals petrified in the same manner, are to be seen in the British Museum,[161]and most public collections: and sliced polished sections, exhibiting the monocotyledonous structure, are common in private cabinets. The endogenous organization of the stems is so obvious as to leave no doubt as to the class to which the trees belong, but M. Brongniart states, that, in the absence of the foliage and fruit, it is seldom possible to pronounce with certainty that a fossil monocotyledonous stem belongs to a Palm; for the internal structure alone does not enable the botanist to fix upon any characters which will distinguish the stems of Palms from those of Pandanus, Agave, Yucca, Aloes, Dracæna, &c. Fossil monocotyledons known by their stems only, are therefore arranged by M. Brongniart under the general name ofEndogenites.

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