Chapter 10

[115]Figured in Bd. pl. lvi.

InMegaphyton, the large ovate scars indicate the attachment of deciduous branches or gigantic leaves, which did not grow all round the stem, but in a regular order of superposition on each side.[116]

[116]Figured in Pict. Atlas, pl. xxv.

ASTEROPHYLLITES.

Asterophyllites.—I shall conclude this notice of some of the most characteristic trees of the Carboniferous Flora, with an account of a tribe of plants whose remains are socommon in the coal-shales and grits, that there are but few large slabs with vegetable remains that do not exhibit examples of the elegant verticillate foliage of one or more species. The termAsterophyllites, (expressive of the star-like form of the leaves,) applied to this family by M. Ad. Brongniart, includes several fossil plants which are known to geologists under different generic names; the following concise account may be useful to the student.[117]

[117]ConsultTableau des Genres de Végétaux Fossiles, par M. Ad. Brongniart. Diet. d'Hist. Nat. Paris, 1849.

1.Calamodendron.—These are arborescent stems, ligneous internally, and covered with a smooth carbonaceous crust, without regular longitudinal striæ, and not articulated; but the woody axis covered by this bark is deeply striated and articulated, resembling in this respect the true Calamites. These stems have a large central pith, or medullary column, surrounded by a ligneous zone, which is formed of radiated bands, without circles of growth: the structure of the carbonized bark is unknown.

2.Asterophyllites.—These are supposed to be the branches and foliage of the stems above described.

3.Sphenophyllum.—Plants, differing in the form of the leaves, but analogous in structure and mode of fructification to the Asterophyllites.

4.Annularia.—Herbaceous aquatic plants, distinct from the preceding.

5.Volkmannia.—These fossil plants are Asterophyllites in fructification.

TheAsterophyllites(Lign.42) had branched articulated stems, with verticillate leaves, arranged perpendicularly to the branches which supported them: but as the foliage is in most instances partially concealed, the natural form is but seldom observable.

The original plants are supposed to have been a tribe offlowering dicotyledons, for small seed-vessels resembling those of the Cypress are often found with the foliage.

Lign. 42.Asterophyllites equisetiformis;nat.Coal-shale.(Foss. Flor.)

ANNULARIA CARDIOCARPON.

TheAnnulariæwere herbaceous plants with verticillate foliage like the former, but the whorls were arranged on the same plane with the stems on which they grew, and their remains have a very elegant appearance when expanded in the coal schists. It is supposed that they were aquatic plants, and that the stems and leaves floated on the surface of the water.[118]

[118]Wond.p. 717. Petrifactions, pp. 27, 43, &c. For coloured figures see Pictorial Atlas, pl. v.

Sphenophyllum(wedge-shaped leaf).Lign. 43.—The fossil vegetables thus named, though somewhat resembling in their elegant verticillate foliage the Asterophyllites, differ essentially, and are regarded by M. Brongniart as herbaceous plants related to theMarsiliaceæ, or Pepper-worts. The leaves are triangular, truncated at the summit, and very deeply lobed and dentated. The fructification consists of sessile axillary or terminal spikes, composed of verticillate bracteæ, covering the receptacles. This mode of fructification resembles that of the Asterophyllites.[119]

[119]For details consultTab. des Genres de Vég. Foss.p. 52.

Cardiocarpon.—Lign. 44. fig. 1.—These are small fossilfruits or seed-vessels, which much resemble those of the Thuja orArbor-vitæ, and are so often found imbedded with masses of the foliage of Asterophyllites, that it is conjectured they belong to those plants. They occur in groups of from five to twenty, and evidently weredidymous,i.e.grew in pairs.Fig. 1a. is an enlarged view, to show the surface left by the attachment of the twin-seed.

Lign. 43.Fig.1.—Sphenophyllum Schlotheimii;nat.2.—Sphenophyllum erosum.Coal-Shale.

Coal-Shale.

Trigonocarpum.Lign. 44. figs. 3. 4.—These fruits, which resemble those of certain Palms, are often met with in the coal-mines of Leicestershire and Yorkshire; frequently occurring in groups of thirty or forty, as if they were the scattered seeds of a raceme of a Palm: they are referred to the genus Nœggerathia, a tree of the carboniferous formation allied to the Palms.

FOSSIL FRUITS.

A figure of a fossil fruit from the Oolite—Carpolithes Bucklandi, is introduced inLign. 44, fig. 2, and will be described hereafter.

Lign. 44. Fossil Fruits, or Seed-vessels;nat.Fig.1.—Cardiocarpon acutum.Snibstone Coal-mine, Leicestershire.1a.—1a.—One of the above magnified.2.—2.—Carpolithes Bucklandii.Coralline Oolite, Malton.3.—Trigonocarpum olivæforme.Snibstone Colliery.4.—Trigonocarpum Nöggerathi.

The reader will observe that the fossil vegetables hitherto described belong, with but few exceptions, to the Carboniferous flora; and that the remains of Ferns, Calamites, Sigillariæ, and Lepidodendra, compose in a great measure those prodigious accumulations of mineral fuel, or coal, which supply the luxuries and necessities created by civilization.

Our review of fossil plants will now assume somewhat of a botanical arrangement, and we proceed to notice some of the most characteristic vegetable forms of the secondary and tertiary formations. We commence our examination with those remarkable tribes of gymnosperms, the Cycadaceæ, which comprise the Zamiæ and Cycadeæ.

Fossil Cycadaceæ.

The plants of this subdivision of the vegetable kingdom, from their singular structure and mode of growth, their simple cylindrical stems, and coronets of pinnated foliage, resembling that of certain palms, their usually gyrate vernation like that of the ferns, and their anomalous inflorescence and fructification, are objects of great interest to the scientific botanist; while the abundance of their fossil remains in the secondary formations renders them of the highest importance to the geologist.

Lign. 45.Foliage and upper part of the Stem of Cycas revoluta1/12nat.In Kew Conservatory.

As many kinds of Zamia[120]and Cycas are cultivated in our hot-houses, the general appearance of the plants of this order must be familiar to the reader: the annexed figure of a beautiful living Cycas in the Royal Gardens at Kew, will serve to illustrate the general aspect of these exotics.

[120]The Linnæan genus Zamia is now separated into five or six genera, as Encephalartos, Macrozamia, Dion, &c.

The Zamiæ are short plants, with stout cylindrical stems, beset with thick scales, which are the bases of the petioles that have been shed: towards the summit the stem is garnished with a crown of elegant leaves; the fruit resembles the cones of pines. The leaves are pinnated, and very tough; their venation is either parallel as in endogens, or dichotomous as in ferns, but never reticulated as in exogens:in a young state they are coiled up like a crosier, as in ferns.

The Cycadeæ have the general aspect of the Zamiæ, but differ in their fructification and other characters; and some species have the stem bifurcated towards the top, and attain a height of upwards of twenty feet; for example,C. circinalis.

The stem in its internal structure[121]bears a close analogy to that of the Coniferæ; it has a central medullary column surrounded by a ligneous cylinder, divided by cellular medullary rays, each composed of bundles of vessels, and a thick cellular cortical investment or false-bark,[122]composed of the persistent scales that formed the bases of the petioles. (SeePl. V. fig. 5.)

[121]SeeBd.pl. lxii.[122]SeeBd.vol. i. pp. 494-498, for detailed description of structure in recent and fossil Zamiæ and Cycadeæ.

[121]SeeBd.pl. lxii.

[122]SeeBd.vol. i. pp. 494-498, for detailed description of structure in recent and fossil Zamiæ and Cycadeæ.

The existing species of Cycadaceæ are exclusively natives of hot regions, and chiefly inhabit the West Indies, South Africa, Equinoctial America, Japan, New Holland, &c.; not one species is known in Europe: a fact in striking contrast with the abundance of fossil plants of this order, which occur throughout the secondary formations of England and the continent.[123]

[123]The most interesting collection of living Cycadeæ and Zamiæ near London, is that ofJames Yates, Esq., of Lauderdale House, Highgate; it comprises choice examples of several of the sub-genera into which these plants are now divided by botanists.

No true cycads have hitherto been discovered in the carboniferous deposits; it is in the floras of the secondary epochs, from the new Red to the Cretaceous inclusive, that this tribe of plants forms an important feature. The foliage, stems, and fruits, occur in a fossil state; and as these organs cannot be referred with certainty to their respective plants, distinct genera are formed for their reception.

Foliage.—From the tough and durable nature of the leaves, the foliage of the Cycadeæ occurs in a fine state ofpreservation; and in the fluvio-marine deposits of the Oolite of Yorkshire, many specimens of great beauty have been collected. I know not another locality in England so rich in fossils of this kind, as the cliffs along the coast near Scarborough; Gristhorpe Bay is well known to collectors. Not only the leaves, but also the fruits or cones occur, and of these, examples are to be seen in most public museums.[124]The leaves are carbonized, but the venation is well preserved.

[124]British Museum: see Petrifactions, p. 54, Room 1, Case F.

The leaflet of the recent Cycas is distinguished by a strong nervure, which runs along the middle; that of Zamia has no midrib, but fine parallel veins that pass direct to the margin.

Lign. 46.Part of a leaf ofPterophyllum comptum;nat.Oolite, Scarborough.

Lign. 47.Part of a leaf ofZamites pectinatus;nat.Oolite, Stonesfield.

Pterophyllum comptum.Lign.46.—The general aspect of these fossils is shown in this figure of a leaf, referred to the genusPterophyllum, which is characterized by leaflets, often slightly united at their base, truncated at the summit, of a quadrangular or oblong form, and having fine, straight, parallel veins. The leaves are ten or twelve inches long, and have fine lanceolate leaflets; they are abundant in the same beds, and are often associated with the cones or fruit[125]figured inLign.48.

[125]Brit. Mus. Petrifactions, p. 55.

ZAMITES PECTINATUS.

Zamites pectinatus.Lign. 47.—In the Stonesfield slate, collocated with remains of reptiles, fishes, insects, and mollusks, leaves and fruits of cycads are occasionally met with.A portion of a leaf nine inches long is here figured. The Lias of Dorsetshire has yielded many beautiful relics of this family[126]

[126]In the carboniferous strata of Eastern Virginia, United States, which are referred by Professor Rogers to the Oolitic epoch, leaves of Cycadeous plants are abundant. See Trans. American Geol p. 298.

But few vestiges of the foliage of Cycads have been observed in the Wealden formation of England; one elegant leaf, however, of an undescribed species, was obtained some years since, from a sandstone quarry in Surrey, and is figured in my Geology of the South-east of England, p. 238; it is named in honour of my distinguished friend, M. Ad. Brongniart,Cycadites Brongniarti. The Wealden of the north of Germany is very rich in fossil Cycadeæ; my friend. Dr. Dunker, has figured and described twelve species in his admirable work on the organic remains of that formation.[127]

[127]Mon. Norddeutschen Weald, tab. i. to vii.

Fruits.—The cones or fruits which occur with the foliage of Zamiæ in the carbonaceous shales and marls of the Oolite of the Yorkshire coast, are very fine, and have been described under the various names ofZamites Mantelli,Z. gigas, andZ. lanceolatus.

An interesting memoir on the structure of these fossils, by James Yates, Esq. (a gentleman distinguished for his knowledge of the recent Cycadaceæ), is published in theProceedings of the Yorkshire Philosophical Society for 1849, p. 37; and another communication on the same subject by my friend Professor Williamson, of Manchester, inYork. Phil. Trans.1819, p. 45; to these papers I must refer for a detailed account of all that is at present known respecting their organization.

Lign. 48. Fruit of Zamites Mantelli, (Brongniart);nat.From near Scarborough.The surface of the cone is concealed by the bracteæ.

Zamites Mantelli.[128]Lign.48.—The leaves associated with the fruit here figured, have lanceolate leaflets that insensibly contract at the base, and are inserted obliquelyinto the rachis; thus resembling the foliage of the recentEncephalartos. With these leaves, and the ovate cones (Lign.48), are occasionally found a circle of leaves or elongated scales, locally termed "collars," which Professor Williamson has shown to be a zone formed by a scaly bud in which the germ of the plants was inclosed. In the progress of development, the fruit burst through the upper part of the investing sheath, and, as it grew to maturity, rose above the incurved elongated bracteæ, till the latter formed a zone or "collar" around the pedicle of the cone.[129]These fossils have been mistaken for flowers.[130]

[128]Podozamitesof Braun.[129]Proc. Yorkshire Philos. Soc. 1849, p. 45.[130]Bird's Yorkshire, tab. i. figs. 1 and 7.

[128]Podozamitesof Braun.

[129]Proc. Yorkshire Philos. Soc. 1849, p. 45.

[130]Bird's Yorkshire, tab. i. figs. 1 and 7.

It does not appear that the structure of the cone has been preserved in any of the specimens, so as to demonstrate the characters of the original; in all those I have examined, the surface of the fruit is concealed by the elongated bracteæ, which are pressed flat, and adhere so firmly to the inclosed body, as to render it impossible to ascertain its nature.[131]Mr. Williamson is of opinion that the plant resembled the recentCycas circinalis, in its great height, and lax habits; and states, that he had seen portions of leaves that were three feet in length.

[131]Brit. Mus. Petrif. p. 55.

Zamites crassus.Lign. 49, fig. 1.—In Sandown Bay, on the south coast of the Isle of Wight, where the Wealden beds rise to the surface from beneath the lowest strata of Greensand on the east and west, several cones have been found, associated with other vegetable remains, and bones of the Iguanodon, &c. A fossil cone from this locality is here figured; it bears considerable resemblance to the fruit of the recentEncephalartos.

ZAMITES OVATUS.

Zamites ovatus.Lign. 49, fig. 2.—A few examples of cycadeous fruits have been collected from the Greensand of Kent and Sussex. The beautiful fossil represented,Lign. 49, fig. 2, from Foss. Flor. is referred to the Zamiæ, bythe eminent authors of that work; but it presents in its imbricated character a greater analogy to a pine cone.

Lign. 49. Fossil Fruits of Cycadeous Plants;1/2nat.Fig.1.—Zamites Crassus.Wealden, Isle of Wight.2.—Zamites Ovatus.Greensand, Kent.

Zamites Sussexiensis.—At Willingdon, near Eastbourn, in Sussex, a cone nearly six inches long was discovered in a bed of Greensand, which abounds in fossil coniferous wood: it is of an elongated cylindrical form, and covered with hexagonal scales. I have provisionally named itZamites Sussexiensis(Geol. Proc. 1843), as it presents a nearer resemblance to the fruit of Zamiæ than to that of Conifers.

Trunks and Stems of Cycadaceæ.—In this section I shall notice the fossil plants which occur so abundantly in the fresh-water deposits that overlie the marine oolitic limestone of the Isle of Portland, and which must be familiar to my readers, from the graphic account of the circumstances under which they occur, by Mr. Webster, and subsequently by Dr. Buckland, and Sir H. De la Beche. In my Wonders of Geology, p. 387, and Geol. Isle of Wight, p. 395, the geological phenomena of that most interesting locality,the Isle of Portland, are so fully described, that it will not be necessary to dwell upon them; the structure and affinities of the fossil vegetables are the especial objects of our present inquiry.

MANTELLIA NIDIFORMIS.

Lign. 50. Silicified Trunk of Mantellia nidiformis(Brongn.);1/4nat.(Cycadites megalophyllus.Bd.)Wealden. Isle of Portland.a.Central mass of cellular tissue,b.Circle of ligneous plates,c.Zone of cellular tissue,d.False-bark.

Mantellia.Lign.50,51.—The fossil Cycadeæ of the Isle of Portland were first described botanically by Dr. Buckland, (Geol. Trans, vol. ii. 2d Series,) under the name ofCycadeoidea; of which Memoir the account inBd.p. 404, is an abstract. M. Ad. Brongniart, considering these plants as a peculiar type, referred them to a new genus, which he did me the honour to nameMantellia(Prod. Veg. Foss.). These stems or trunks are from one to two feet in height; the circumference of the largest not exceeding three feet. The stem issubcylindrical, and the external surface covered with the rhomboidal scars formed by the attachment of the leaf-stalks, and which are widest in their transverse diameter.

There are two species, which are readily distinguished by the form of the stems, and the difference in the size of the cicatrices left by the petioles.

The most common kind is short, and spheroidal, and the leaf-scars are relatively large; its shape has caused it to be named "Crows' nest," by the quarrymen, who believe these plants to be nests that were built by crows in the trees of the petrified forest with which they are imbedded. The specific name (nidiformis) adopted by M. Brongniart, expresses this popular notion.

Lign. 50.represents a fine example from the Portland Dirt-bed, which exhibits a structure altogether similar to that which characterizes the stems of recent cycadeous plants; namely, (a) a central mass of cellular tissue surrounded by circles of laminated ligneous rays or plates (b); then a zone of cellular tissue (c), and an external cylinder of false-bark (d). The mode of increase by buds, from germs in the axillæ of the petioles, as in the living plants, is also distinctly seen.

Lign. 51. Mantellia cylindrica.(Brongn.);1/8nat.(Cycadites microphyllus. Bd.)Wealden. Petrified Forest of the Isle of Portland.

The other species is subcylindrical, and the leaf-scars are much smaller and more regular than inM. nidiformis, indicating a more delicate foliage, as expressed by Buckland's specific name: that of M. Brongniart refers to the cylindrical form of the stem. This plant was higher and more slender than its associate. Numerous buds are seen in the axillæ of the petioles in the specimen figured.

These fossils present, both externally and internally, a close relation to the bulbiform stems of the recent Cycadeæ, namedEncephalartos, of South Africa.[132]

[132]The fossil Cycads of the Isle of Portland are admirably described and illustrated in Dr. Buckland's Bridgewater Essay, (p. 497, and pl. lx. lxi.), and their internal structure is fully explained.

Neither the leaves nor the fruit are known: a cone found in the Dirt-bed of Portland, and attributed to these plants, appears to belong to the coniferæ of the petrified forest. Examples of Mantelliæ have been found in the quarry of Portland-stone at Swindon, Wilts.

CLATHRARIA LYELLII.

Lign. 52. Clathraria Lyellii.Wealden.A branched example of the inner axis: the original 31/2feet high.

Clathraria[133]Lyellii.Lign.52-57.—The fossil plants to which I would next direct attention were first discovered by me in the Wealden strata of Sussex, in 1820, and were figured and described under the name they still bear, in my Fossils of Tilgate Forest, in 1827. The specimens figured in that work are the most illustrative hitherto discovered, with but one exception.[134]

[133]Clathraria,i.e.lattice stem, from the scars left by the petioles.[134]They are now in the British Museum; see Petrifactions, p. 45.RoomI.CaseE.

[133]Clathraria,i.e.lattice stem, from the scars left by the petioles.

[134]They are now in the British Museum; see Petrifactions, p. 45.RoomI.CaseE.

From the imperfect state of the remains of these plants, the structure and affinities of the originals were very ambiguous, and the fossils have been placed by some eminent botanists with the Liliaceæ, and by others with the Asphodeleæ; their true botanical position is doubtless with the Cycadaceæ; for in some points they resemble the Zamiæ, in others the Cycadeæ.

The stem of the Clathraria is composed of a solid internal axis, the surface of which is covered with reticulated fibres; the large branched specimen of this part, figured inLign. 52, is the finest example hitherto obtained: it was discovered, with bones of the Iguanodon, in a quarry near Cuckfield, Sussex, in 1820. The axis is invested with a very thick false-bark, formed of the consolidated bases of the leaf-stalks, the insertions of which are rhomboidal and transverse. The outer surface of the bark is consequently marked with elevated lozenge-shaped cicatrices (Lign. 53), separated from each other by a marginal furrow, which is surrounded by a parallel ridge or band of a fibrous structure.

Lign. 53. Clathraria Lyellii.1/4nat.A stem, with rhomboidal transverse scars, left by the petioles; broken transversely and separated, to show the internal axis ata, which, if the pieces were united, would be received in the cavity below the depression, or cicatrix, on the middle of the upper portion,b, was probably the situation of a resinous secretion, like the dragon-blood in the Dracæna.

The cortical zone is generally converted into a cylinder of stone, which in some examples separates from the axis. In a beautiful specimen of this kind,Lign. 54, the axis projects and is surrounded by the false-bark.

The axis is solid, and has its surface strongly marked with interrupted ridges. This surface has generally patches of vascular tissue adhering to it; and there are here and there deep pits, or lacunæ, which probably contained a resinous secretion. Thin transverse sections of the axis, prepared with Canada balsam, and examined under the microscope, only give faint traces of cellular tissue.

Lign. 54. Clathraria Lyellii;1/4nat.Wealden Sandstone.Tilgate Forest.Portion of a stem, scored by the cicatrices of the petioles;showing the Axisa, surrounded by the cortical cylinder.

Lign. 55.Petiole of Clathraria Lyellii;a.External aspect.b.Inner surface.c.Vascular pits left by the separationof the leaf.

I have spared neither trouble nor expense in endeavouring to detect the organization of this plant; numerous sections of stems have been cut, and examined microscopically, but very few exhibit any traces of structure; and in those which retain some vestiges of organization, the siliceous mass which permeates the vascular tissue, is not sufficiently transparent to yield satisfactory results. It can only be inferred that in their internal organization, as in their external characters, the Clathrariæ were most nearly allied to the Cycadeæ or Zamiæ. A remarkable specimen, (Lign. 56,) discovered in a stratum of Chalk-marl, near Bonchurch, confirms this view, and throws much light on the nature and relations of these vegetables.

This fossil is a portion of the summit of a stem garnished with persistent petioles, or leaf-stalks; it is fifteen inches in length, and nearly perfect at the top; and at the lower end, which has been broken off transversely, the inner axis (Lign. 56 a.), surrounded by the false-bark formed by the confluence and consolidation of the bases of the petioles, is exposed. The stem has been stript of the leaf-stalks at the lowermost part, and exhibits the characteristic lattice-like scars. The petioles are for the most part entire; some of them are abortive, and others, which have supported leaves, are marked on the summits with vascular pits, indicating that the foliagewas shed naturally; as shown inLign. 55 a. These petioles were probably persistent for some years, as in the existing Cycads. The opposite side of the stem to that represented is covered with elongated and flattened petioles.

Lign. 56.Clathraria Lyellii;1/4nat.Chalk-marl. Bonchurch, Isle of Wight.The summit of a stem garnished with petioles; the lower part shows the cicatrices left by the removal of some of the petioles:a, the internal axis.

On the sea-shore bounded by cliffs of Wealden rocks, in the Isle of Wight, water-worn portions of stems of Clathrariæ are occasionally met with; and these are impressed with the lozenge-shaped areas left by the petioles, as in the specimen,Lign. 57. Mr. Saxby, of Bonchurch, has favouredme with the loan of a thin section of a stem of Clathraria in which the bundles of vascular tissue in the petioles appear to be made up of spiral vessels. From what has been advanced, it is obvious that these remarkable plants of the Wealden flora were gymnosperms, closely related to the Cycadeæ.

Vestiges of roots, seed-vessels, and panicles, have been found in the Wealden, which may possibly belong to the Clathraria; but the evidence as to their presumed relationship is at present too vague to require further notice.

Lign. 57.Clathraria Lyellii;1/2nat.Specimen, showing the water-worn external surface.

ENDOGENITES.

Endogenites erosa.—(Geol S. E.pl. i.; Tilg. Foss. pl. iii.; and by Dr. Fitton inGeol. Trans.vol. iv.)—The genusEndogeniteswas established by M. Ad. Brongniart for the reception of those fossil stems and woods, whose internal structure is endogenous, but which are too imperfect to be referred to any particular family. In this category must be placed certain silicified stems having a carbonaceous cortical investment, which I discovered in the strata of Tilgate Forest, in 1820.

These fossils often occur in the layers of lignite which traverse the clay-beds in some parts of the Weald of Sussex. They are from one to eight inches in diameter, and five or six feet in length, and of very irregular shapes; I have not observed any indications of branches. Some specimens are subcylindrical in the middle, and gradually taper to a point at each end; others are of a depressed clavated form, like some of the Cacteæ or Euphorbiaceæ. They are generally silicified,and, whenin situ, are invested with a friable carbonaceous crust, of a glossy lustre, which soon falls to pieces on exposure to the atmosphere, so that cabinet specimens seldom retain any vestiges of it. When this coaly matter is removed, the surface of the silicified stem is seen to be traversed by numerous fine meandering grooves, and deep, tortuous channels, disposed in an irregular manner, in a longitudinal direction. These channels or vessels, which are generally lined with quartz crystals, give the surface that eroded appearance which suggested the specific name, erosa; but this term is inapplicable, for the perforations and sinuosities are not the effect of erosion, but result from the structure of the original. Polished sections, seen by transmitted light, are represented in Dr. Fitton's memoir (Geol. Trans.vol. iv.); and I have had many slices ground as thin as possible, in the hope of detecting the characters of the vascular tissue. In one example there are indications of a cycadeous structure, which favour the conclusion, that the originals belonged to an extinct tribe of gymnosperms; but in other specimens, bundles of vascular tissue, resembling those of palms, are apparent.

Large water-worn stems ofEndogenitesare occasionally washed out of the Wealden cliffs at Hastings, and in Sandown and Brook Bays, in the Isle of Wight.

Fossil coniferæ.

FOSSIL CONIFERÆ.

The other great natural order of Gymnospermous phanerogamiæ,[135]theConiferæ, or cone-bearing—so named from the form of their fruit, of which the fir-cones and larch-juli are familiar examples,—comprise the extensive tribes of Firs and Pines, and the Cypresses, Yews, Junipers, Cedars, &c., among which are the loftiest trees on the face of the globe.

[135]Signifying, flowering plants with naked seeds.

The Conifers are all arborescent, having numerous branches, which are in general disposed with much regularity. The leaves are commonly acicular or needle-shaped, narrow, and linear: in two or three genera, however, (Dammara,Podocarpus,) the foliage departs remarkably from the ordinary type, the leaves being broad and flat. The structure of the stem, though in its general characters essentially exogenous (seePlate IV. fig. 4),—that is, having a central pith, medullary rays, zones of vascular tissue, and concentric circles of growth,—differs in the almost entire absence of spiral vessels, and in the peculiar modification of the radiating bands of woody fibre, which are made up of uniform longitudinal vessels, and run parallel with the medullary rays. The lateral walls of these vessels have longitudinal rows of areolæ, which are generally circular or elliptical, but when in contact are angular and polygonal: each areola has a small pore or punctation in the centre. These discs, glands, or ducts, as they are called, are variously arranged in different genera; they are generally confined to the contiguous and corresponding lateral surfaces of the fibres; and occur rarely, if ever, on the inner and outer aspects of the vessels. In the recent genus Pinus the rows of ducts are single in some species; in others both single and double series occur, but never more than two, and in the latter case the ducts are always parallel to each other (see pl. v. 3b.Wond.pp. 696, 725). But in theAraucariæ, or Norfolk Island Pines, the vessels have double, triple, and sometimes quadruple, rows of discs, of smaller size than in the common pines; and in the double series, these bodies are always arranged alternately (Wond.p. 696.Bd.56a.); Mr. Nicol states that there are about 50 discs in the length of1/20inch, the diameter of each not exceeding1/1000inch.

The form and arrangement of these ducts, and the structure of the medullary rays, are the characters on which the scientific botanist relies for the detection of the affinities ofthe coniferous trees, whose mineralized trunks and branches, in a fragmentary state, are, for the most part, the only relics of these important tribes of the lost floras of the earlier ages of our planet.[136]

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