Chapter XVII: Part II (1)

In the noble flora of the Coal Measures much still remains to be done in Scotland. Our Lower Carboniferous rocks are of immense development; the Limestones of Burdiehouse, with their numerous terrestrial plants, occur many hundred feet beneath our Mountain Limestones; and our list of vegetable species peculiar to these lower deposits is still very incomplete. Even in those higher Carboniferous rocks with which the many coal workings of the country have rendered us comparatively familiar, there appears to be still a good deal of the new and the unknown to repay the labor of future exploration. It was only last year that Mr. Gourlay[53] of this city (Glasgow) added to our fossil flora a new Volkmannia from the coal field of Carluke; and I detected very recently in a neighboring locality (the Airdrie coal field), though in but an indifferent state of keeping, what seems to be a new and very peculiar fern. It presents at first sight more the appearance of a Cycadaceous frond than any other vegetable organism of the Carboniferous age which I have yet seen. From a mid stem there proceed at right angles, and in alternate order, a series of sessile, lanceolate, acute leaflets, nearly two inches in length by about an eighth part of an inch in breadth, and about three lines apart. Each is furnished with a slender midrib; and, what seems a singular, though not entirely unique, feature in a fern, their edges are densely hirsute, and bristle with thick, short hair, nearly as stiff as prickles. The venation is not distinctly preserved; but enough remains to show that it must have been peculiar,--apparently radiating outwards from a series of centres ranged along the midrib. Nay, the apparent hairs seem to be but prolongations of the nerves carried beyond the edges of the leaflets. There is a Stigmaria, too, on the table, very ornate in its sculpture, of which I have now found three specimens in a quarry of the Lower Coal Measures near Portobello, that has still to be figured and described. In this richly ornamented Stigmaria the characteristic areolæ present the ordinary aspect. Each, however, forms the centre of a sculptured star, consisting of from eighteen to twenty rays, or rather the centre of a sculptured flower of the composite order, resembling a meadow daisy or sea-aster. The minute petals,--if we are to accept the latter comparison,--are of an irregularly lenticular form, generally entire, but in some instances ranged in two, or even three, concentric lines round the depressed centre of the areolæ; while the interspaces outside are occupied by numerous fretted markings, resembling broken fragments of petals, which, though less regularly ranged than the others, are effective in imparting a richly ornate aspect to the whole.

STIGMARIA.]

THE SAME, MAGNIFIED.]

Ever since the appearance, in 1846, of Mr. Binney's paper on the relations of stigmaria to sigillaria as roots and stems, I have been looking for distinguishing specific marks among the former; and, failing for a time to find any, I concluded that, though the stems of the sigillarian genus were variously sculptured, their roots might in all the species have been the same. The present rich specimen does seem, however, to bear the specific stamp; and, from the peculiar character of the termination of another specimen on the table, I am inclined to hold that the stigmaria may have borne the appearance rather of underground stems than of proper roots. This specimen suddenly terminates, at a thickness of two and a half inches, in a rounded point, abrupt as that of one of the massier cacti; and every part of the blunt sudden termination is thickly fretted over with the characteristic areolæ. The slim tubular rootlets must have stuck out on every side from the obtuse rounded termination of this underground stem, as we see, on a small scale, the leaflets of our larger club mosses sticking out from what are comparatively the scarce less abrupt terminations of their creeping stems and branches. In at least certain stages of growth the sub-ærial stems of Lepidodendron also terminated abruptly (see Fig. 24); and the only terminal point of Ulodendron I ever saw was nearly as obtuse as that of Stigmaria.

STIGMARIA.]

I have been long desirous of acquainting myself with the true character of this latter plant (Ulodendron), but hitherto my labors have not been very successful. A specimen of _Ulodendron minus_, however, now on the table, which I disinterred several years ago from out a bed of ferruginous shale in the Water of Leith, a little above the village of Colinton, exhibits several peculiarities which, so far as I know, have not yet been described. Though rather less than ten inches in length by about three inches in breadth, it exhibits no fewer than seven of those round, beautifully sculptured scars, ranged rectilinearly along the trunk, by which this ancient genus is so remarkably characterized. It is covered with small, sharply relieved, obovate scales, most of them furnished with an apparent midrib, and with their edges slightly turned up; from which peculiarities, and their great beauty, they seem suited to remind the architect of that style of sculpture adopted by Palladio from his master Vitruvius, when, in ornamenting the Corinthian and composite torus, lie fretted it into closely imbricated obovate leaves. These scales are ranged in elegant curves, not unlike those ornamental curves,--a feat of the turning-lathe,--which one sees roughening the backs of ladies' watches of French manufacture. My fossil exhibited, as it lay in the rock, what I never saw in any other specimen,--a true branch sticking out at an acute angle from the stem, and fretted with scales of a peculiar form, which in one little corner appear also on the main stem, but which differ so considerably from those of the obovate, apparently imbricated type, that, if found on a separate specimen, they might be held to indicate difference of species. It has been shown by Messrs. Lindley and Hutton, on the evidence of one of the specimens figured in the "Fossil Flora," that the line of circular scars so remarkable in this genus, and which is held to be the impressions made by a rectilinear range of almost sessile cones, existed in duplicate on each stem,--a row occurring on two of the sides of the plant directly opposite each other. The branch in my specimen struck off from one of the intermediate sides at right angles with the cones. We already know that these were ranged in one plane; nor, if the branches were ranged in one plane also,--certainly the disposition of branch which would consort best with such a disposition of cone,--would the arrangement be without example in the vegetable kingdom as it even now exists. "Our host," says the late Captain Basil Hall, in his brief description of the island of Java, "carried us to see a singular tree, which had been brought from Madagascar, called familiarly the _Traveller's Friend_, Urania being, I believe, its botanic name. We found it to differ from most other trees in having all its branches in one plane, like the sticks of a fan or the feathers of a peacock's tail." I may further mention, that the specimen which showed me the abrupt cactus-like terminations of Ulodendron repeated the evidence of Messrs. Lindley and Hutton's specimen regarding the arrangement of the cone scars on opposite sides, and showed also that these scars ascended to within little more than an inch of the top of the plant.

As there are cases in which the _position_ of a fossil plant may add, from its bearing on geologic history, a threefold interest to the fossil itself, regarded simply as an organism, I may be permitted to refer to a circumstance already recorded, that there was a well marked Bechera detected about two years ago by Dr. Macbean of Edinburgh, an accomplished naturalist and careful observer, in a thin argillaceous stratum, interposed, in the Queen's Park, between a bed of columnar basalt and a bed of trap-tuff, in the side of the eminence occupied atop by the ruins of St. Anthony's Chapel. The stratified bed in which it occurs seems, from its texture and color, to be composed mainly of trappean materials, but deposited and arranged in water; and abounds in carbonaceous markings, usually in so imperfect a state of keeping that, though long known to some of the Edinburgh geologists, not a single species, or even genus, were they able to determine. All that could be said was, that they seemed fucoidal, and might of course belong to any age. The Bechera, however, shows that the deposit is one of the Lower Coal Measures. There was found associated with it a tooth of a Carboniferous Holoptychius, whose evidence bore out the same conclusion; and both fossils derive an importance from the light which they throw on the age of the bed of tuff which underlies the stratum in which they occur. At least this trap-rock must be as old as the fossiliferous layer which rests upon it, or rather, as shown by its underlying position, a little older: it must be a trap of the earlier Carboniferous period. Further, it must have been, not injected among the strata, but poured out over the surface,--in all probability covered at the time by water; and there must have formed over it, ere another overflow of trap took place, a thin sedimentary bed charged with fragments of the plants of the period, and visited, when in the course of deposition, by some of its fishes.

SPHENOPTERIS BIFIDA.

(_Burdiehouse._)]

Even among the vegetable organisms of our Coal Measures, already partially described and figured, much remains to be accomplished in the way of restoration. Portions of _Sphenopteris bifida_, for instance, a fern of the Lower Carboniferous rocks have been repeatedly figured; but a beautiful specimen on the table, which exhibits what seems to be the complete frond of the plant, will give, I doubt not, fresh ideas respecting the general framework, if I may so speak, of this skeleton fern, to even those best acquainted with the figures; and an elaborate restoration of its contemporary, _Sphenopteris affinis_ (see frontispiece) which I completed from a fine series of specimens in my collection, will be new, as a whole, to those most familiar with this commonest of the Burdiehouse fossils. From comparisons instituted between minute portions of this Sphenopteris and a recent fern, it has been held considerably to resemble a Davallia of the West Indies; whereas it will be seen from the entire frond that it was characterized by very striking peculiarities, exemplified, say some of our higher botanical authorities, to whom I have submitted my restoration, by no fern that now lives. The frond of _Davallia Canariensis_, though unlike in its venation, greatly resembles in general outline one of the larger pinnæ of _Sphenopteris affinis_; but these pinnæ form only a small part of the entire frond of this Sphenopteris. It was furnished with a stout leafless rachis, or leaf-stalk, exceedingly similar in form to that of our common brake (_Pteris aquilina_). So completely, indeed, did it exhibit the same club-like, slightly bent termination, the same gradual diminution in thickness, and the same smooth surface, that one accustomed to see this part of the bracken used as a thatch can scarce doubt that the stipes of Sphenopteris would have served the purpose equally well; nay, that were it still in existence to be so employed, a roof thatched with it, on which the pinnæ and leaflets were concealed, and only the club-like stems exposed, row above row, in the style of the fern-thatcher, could not be distinguished, so far as form and size went, from a roof thatched with brake. High above the club-like termination of the rachis the stem divided into two parts, each of which, a little higher up, also divided into two; these in turn, in at least the larger fronds, also bifurcated; and this law of bifurcation,--a marked, mayhap unique, peculiarity in a fern,--regulated all the larger divisions of the frond, though its smaller pinnæ and leaflets were alternate. It was a further peculiarity of the plant that, unlike the brake, it threw off, ere the main divisions of its rachis took place, two pinnæ placed in the alternate order, and of comparatively small size. The frond of _Sphenopteris bifida_ was of a more simple form than that of its larger congener, and not a little resembled a living fern of New Zealand, _Coenopteris vivipara_. It was tripinnate; its secondary stems were placed directly opposite on the midrib, but its tertiary ones in the alternate arrangement; and its leaflets which were also alternate, were as rectilinear and slim as mere veins, or as the thread-like leaflets of asparagus. Like the fronds of Coenopteris when not in seed, it must have presented the appearance of the mere macerated framework of a fern. I need scarce remark that, independently of the scientific interest which must attach to restorations of these early plants, they speak powerfully to the imagination, and supply it with materials from which to construct the vanished landscapes of the Carboniferous ages. From one such restored fern as the two now submitted to the Association, it is not difficult to pass in fancy to the dank slopes of the ancient land of the Lower Coal Measures, when they waved as thickly with graceful Sphenopteres as our existing hill sides with the common brake; and when every breeze that rustled through the old forests bent in mimic waves their slim flexible stems and light and graceful foliage.

In 1844, when Professor Nicol, of Marischal College, Aberdeen, appended to his interesting "Guide to the Geology of Scotland," a list of the Scottish fossils known at the time, he enumerated only two vegetable species of the Scotch Oolitic system,--_Equisetum columnare_ and _Pinites_ or _Peuce Eiggensis_; the former one of the early discoveries of our distinguished President, Sir Roderick Murchison; the latter, of the late Mr. William Nicol of Edinburgh. Chiefly from researches in the Lias of Eathie, near Cromarty, and in the Oolites of Sutherland and the Hebrides, I have been enabled to increase the list from two to rather more than fifty species,--not a great number, certainly, regarded as the sole representative of a flora; and yet it may be deemed comparatively not a very small one by such as may remember, that in 1837, when Dr. Buckland published the second edition of his "Bridgewater Treatise," Adolphe Brogniart had enumerated only seventy species of plants as occurring in all the Secondary formations of Europe, from the Chalk to the Trias inclusive. In a paper such as the present I can of course do little more than just indicate a few of the more striking features of the Scottish flora of the middle Secondary ages. Like that of the period of the true Coal, it had its numerous coniferous trees. As shown by the fossil woods of Helmsdale and Eigg, old Oolitic Scotland, like the Scotland of three centuries ago, must have had its mighty forests of pine;[54] and in one respect these trees seem to have more nearly resembled those of the recent pine forests of our country than the trees of the coniferous forests of the remote Carboniferous era. For while we scarce ever find a cone associated with the coniferous woods of the Coal Measures,--Lindley and Hatton never saw but one from all the English coal fields, and Mr. Alexander Bryson of Edinburgh, only one from all the coal fields of Scotland,--tree-cones of at least four different species, more probably of five, are not rare in our Scottish deposits of the Lias and Oolite. It seems not improbable that in the Carboniferous genera Pinites, Pitus, and Anabathra, which approach but remotely to aught that now exists, the place of the ligneous scaly cone may have been taken, as in the junipers and the yews, by a perishable berry; while the Pines and Araucarians of the Oolite were, like their congeners in recent times, in reality coniferous, that is, cone-bearing trees. It is another characteristic of these Secondary conifers, that while the woods of the Palæozoic periods exhibit often, like those of the tropics, none of the dense concentric lines of annual growth which mark the reign of winter, these annual lines are scarce less strongly impressed on the Oolitic woods than on those of Norway or of our own country in the present day. In some of the fossil trees these yearly rings are of great breadth; they seem to have sprung up in the rich soil of sheltered hollows and plains, and to have increased in diameter from half an inch to three quarters of an inch yearly; while in other trees of the same species the yearly zones of growth are singularly narrow,--in some instances little more than half a line in thickness. Rooted on some exposed hill side, in a shallow and meagre soil, they increased their diameter during the twelvemonth little more than a line in the severer seasons, and little more than an eighth part of an inch even when the seasons were most favorable. Further, whether the rings be large or small, we ordinarily find them occurring in the same specimens in groups of larger and smaller. In one of my Helmsdale specimens, indicative generally of rapid growth, there are four contiguous annual rings, which measure in all an inch and two twelfths across, while the four contiguous rings immediately beside them measure only half an inch. "If, at the present day," says a distinguished fossil botanist, "a warm and moist summer produces a broader annual layer than a cold and dry one, and if fossil plants exhibit such appearances as we refer in recent plants to a diversity of summers, then it is reasonable to suppose that a similar diversity formerly prevailed." The same reasoning is of course as applicable to _groups_ of annual layers as to _single_ annual layers; and may we not venture to infer from the almost invariable occurrence of such groups in the woods of this ancient system, that that ill-understood law of the weather which gives us in irregular succession groups of colder and warmer seasons, and whose operation, as Bacon tells us, was first remarked in the provinces of the Netherlands, was as certainly in existence during the ages of the Oolite as at the present time?

CONIFERS?]

CONIFER TWIGS.]

Twigs which exhibit the foliage of these ancient conifers seem to be less rare in our Scotch deposits than in those of England of the same age. My collection contains fossil sprigs, with the slim needle-like leaves attached, of what seem to be from six to seven different species; and it is worthy of notice, that they resemble in the group rather the coniferæ of the southern than those of the northern hemisphere. One sprig in my collection seems scarcely distinguishable from that of the recent _Altingia excelsa_; another, from that of the recent _Altingia cunninghami_. Lindley and Hutton figure in their fossil flora a minute branch of _Dacrydium cupressinum_, in order to show how nearly the twigs of a large tree, from fifty to a hundred feet high, may resemble some of the "fossils referable to Lycopodiaceæ." More than one of the Oolitic twigs in my collection are of a resembling character, and may have belonged either to cone-bearing trees or to club mosses. Respecting, however, the real character of at least one of the specimens,--a minute branch from the Lias of Eathie, with the leaflets attached,--there can be no mistake. The thicker part of the stem is in such a state of keeping, that it presents to the microscope, in a sliced preparation, the internal structure, and exhibits, as in recent coniferous twigs of a year's growth, a central pith, a single ring of reticulated tissue arranged in lines that radiate outwards, and a thin layer of enveloping bark. Nothing, then, can be more certain than that this ancient twig, which must be accepted as representative of the foliage of whole forests of the Secondary ages in Scotland, formed part of a conifer of the Lias; and the foliage of several of the other twigs, its contemporaries, though I have failed to demonstrate their true character in the same way, bear a scarce less coniferous aspect. The cones of the period, from the circumstance that they are locked up in a hard limestone that clings closely around their scales, and from the further circumstance that the semi-calcareous lignite into which they are resolved is softer and less tenacious than the enclosing matrix, present, when laid open, not their outer surfaces, but mere sections of their interior; and give, in consequence, save in their general proportions and outline, but few specific marks by which to distinguish them. We see, however, in some cases in these sections what would be otherwise unseen,--the flat naked seeds lying embedded in their hollow receptacles between the scales, and in as perfect a state of keeping as the seeds of recent pines that had ripened only a twelvemonth ago. Had not the vitality of seeds its limits in time, like life of all other kinds, one might commit these perfect fossil germs to the soil, in the hope of seeing the old extinct forests called, through their agency, a second time into existence. Of three apparent species of cones which occur in the Eathie Lias, the smallest seems to have resembled in size and appearance that of the Scotch fir; the largest, which consisted from bottom to top, as seen in section, of from nine to ten scales, appears to have been more in the proportions of the oblong oval cones of the spruce family; while a cone of intermediate length, but of considerably greater breadth, assumed the rounded form of the cones of the cedar. I have found in the same deposit what seems to be the sprig of a conifer, with four apparently embryo cones attached to it in the alternate order. These are rather more sessile than the young cones of the larch; but the aspect of the whole is that of a larch twig in early summer, when the minute and tender cones, possessed of all the beauty of flowers, first appear along its sides.

ZAMIA.]

ZAMIA.]

Among conifers of the Pine and Araucarian type we mark the first appearance in this system, in at least Scotland, of the genus Thuja. One of the Helmsdale plants of this genus closely resembles the common Arbor Vitæ (_Thuja occidentalis_) of our gardens and shrubberies. It exhibits the same numerous slim, thick-clustered branchlets, covered over by the same minute, sessile, scale-like leaves; and so entirely reminds one of the recent Thuja, that it seems difficult to conceive of it as the member of a flora so ancient as that of the Oolite. But not a few of the Oolitic plants in Scotland bear this modern aspect. The great development of its Cycadaceæ,--an order unknown in our Coal Measures,--also forms a prominent feature of the Oolitic flora. One of the first known genera of this curious order,--the genus Pterophyllum,--appears in the Trias. It distinctively marks the commencement of the Secondary flora, and intimates that the once great Palæozoic flora, after gradually waning throughout the Permian ages, and becoming extinct at their close, had been succeeded by a vegetation altogether new. At least one of the Helmsdale forms of this family is identical with a Yorkshire species already named and figured,--_Zamia pectinata_: a well marked Zamia which occurs in the Lias of Eathie appears to be new. Its pinnate leaves were furnished with a strong woody midrib, so well preserved in the rock, that it yields its internal structure to the microscope. The ribbon-like pinnæ or leaflets were rectilinear, retaining their full breadth until they united to the stem at right angles, but set somewhat awry; and, like several of the recent Zamiæ, they were striped longitudinally with cord-like lines. (Fig. 133.) Even the mode of decay of this Zamia, as shown by the abrupt termination of its leaflets, exactly resembled that of its existing congeners. (Fig. 134.) The withered points of the pinnæ of recent Zamiæ drop off as if clipped across with a pair of scissors; and in fossil fronds of this Zamia of the Lias we find exactly the same clipped-like appearance. (Fig. 135.) Another Scotch Zamia (Fig. 136), which occurs in the Lower Oolite of Helmsdale, resembles the Eathie one in the breadth of its leaflets, but they are not wholly so rectilinear, diminishing slightly towards their base of attachment; they are ranged, too, along the stem or midrib, not at a right angle, but at an acute one; the line of attachment is not set awry, but on the general plane of the leaf; and the midrib itself is considerably less massive and round. A third species from the same locality bears a general resemblance to the latter; but the leaflets are narrower at the base, and, as the print indicates (Fig. 136), so differently attached to the stem, that from the pressure in the rock most of them have become detached; while yet a fourth species (Fig. 137), very closely resembles a Zamia of the Scarborough Oolite,--_Z. lanceolata_. The leaflets, however, contract much more suddenly from their greatest breadth than those of _lanceolata_, into a pseudo-footstalk; and the contraction takes place not almost equally on both sides, as in that species, but almost exclusively on the upper side. And so, provisionally at least, this Helmsdale Zamia may be regarded as specifically new.

CONE.]

With the leaves of the Eathie Zamia, we find, in this northern outlier of the Lias, cones of a peculiar form, which, like the leaves themselves, are still unfigured and undescribed, and some of which could scarce have belonged to any coniferous tree. In one of these (Fig. 138), the ligneous bracts or scales, narrow and long, and gradually tapering till they assume nearly the awl-shaped form, cluster out thick from the base and middle portions of the cone, and, like the involucral appendages of the hazel-nut, or the sepals of the yet unfolded rose-bud, sweep gracefully upwards to the top, where they present at their margins minute denticulations. In another species the bracts are broader, thinner, and more leaf-like: they rise, too, more from the base of the cone, and less from its middle portions; so that the whole must have resembled an enormous bud, with strong woody scales, some of which extended from base to apex. The first described of these two species seems to have been more decidedly a _cone_ than the other; but it is probable that they were both connecting links between such leathern seed-bearing flowers as we find developed in _Cycas revoluta_, and such seed-bearing cones as we find exemplified in _Zamia pungens_. The bud-like cone, however, does not seem to have been that of a Cycadaceous plant, as it occupied evidently not a terminal position on the plant that bore it, like the cones of Zamia or the flowers of Cycas, but a lateral one, like the lateral flowers of some of the Cactus tribe. Another class of vegetable forms, of occasional occurrence in the Helmsdale beds, seems intermediate between the Cycadaceæ and the ferns: at least, so near is the approach to the ordinary fern outline, while retaining the stiff ligneous character of Zamia, that it is scarce less difficult to determine to which of the two orders of plants such organisms belonged, than to decide whether some of the slim graceful sprigs of foliage that occur in the rocks beside them belonged to the conifers or the club mosses. And I am informed by Sir Charles Lyell, that (as some of the existing conifers bear a foliage scarce distinguishable from that of Lycopodiaceæ), so a recently discovered Zamia is furnished with fronds that scarce differ from those of a fern. Even _Zamia pectinata_ may, as Sternberg remarks, have been a fern. Lindley and Hutton place it merely provisionally among the Cycadaceæ, in deference to the judgment of Adolphe Brogniart, and point out its resemblance to _Polypodium pectinatum_; and a small Helmsdale frond which I have placed beside it bears the impress of a character scarce less equivocal. The flora of the Oolite was peculiarly a flora of intermediate forms.

We recognize another characteristic of our Oolitic flora in its simple-leaved fronds, in some of the species not a little resembling those of the recent Scolopendrium, or Hart's-Tongue fern,--a form regarded by Adolphe Brogniart as peculiarly characteristic of his third period of vegetation. These simple ferns are, in the Helmsdale deposits, of three distinct types. There is first a lanceolate leaf, from two and a half to three inches in length, of not unfrequent occurrence, which may have formed, however, only one of the four leaflets, united by their pseudo-footstalks, which compose the frond of Glossopteris,--a distinctive Oolitic genus. There is next a simple ovate lanceolate leaf, from four to five and a half inches in length, which in form and venation, and all save its _thrice_ greater size, not a little resembles the leaflets of a Coal Measure neuropteris,--_N. acuminata_. And, in the third place, there are the simple leaves that in general outline resemble, as I have said, the fronds of the recent Hart's-Tongue fern (_Scolopendrium vulgare_), except that their base is lanceolate, not cordate. Of these last there are two kinds in the beds, representative of two several species, or, as their difference in general aspect and detail is very great, mayhap two several genera. The smaller of the two has a slender midrib, depressed on its upper side, and flanked on each side by a row of minute, slightly elongated protuberances, but elevated on the under side, and flanked by rows of small but well marked grooves, that curve outwards to the edges of the leaf. The larger resemble a Tæniopteris of the English and Continental Oolites, save that its midrib is more massive, its venation less at right angles with the stem, its base more elongated, and its size much greater. Some of the Helmsdale specimens are of gigantic proportions. From, however, a description and figure of a plant of evidently the same genus,--a Tæniopteris of the Virginian Oolite, given by Professor W.B. Rogers of the United States,--I find that some of the American fronds are larger still. My largest leaf from Helmsdale must have been nearly five inches in breadth; and if its proportions were those of some of the smaller ones of apparently the same species from the same locality, it must have measured about thirty inches in length. But fragments of American leaves have been found more than six inches in breadth, and whose length cannot have fallen short of forty inches. The Tæniopteris, as its name bears, is regarded as a fern. From, however, the leathern-like thickness of some of the Sutherland specimens,--from the great massiveness of their midrib,--from the rectilinear simplicity of their fibres,--and, withal, from, in some instances, their great size,--I am much disposed to believe that in our Scotch, mayhap also in the American species, it may have been the frond of some simple-leaved Cycas or Zamia. But the point is one which it must be left for the future satisfactorily to settle; though provisionally I may be permitted to regard these leaves as belonging to some Cycadaceous plant, whose fronds, in their venation and form, resembled the simple fronds of Scolopendrium, just as the leaves of some of its congeners resembled the fronds of the pinnate ferns.

I have already referred to the close resemblance which certain Cycadaceous genera bear to certain of the fern family. In at least two species of Pterophyllum,--_P. comptum_ and _P. minus_,--the divisions of the leaflets seem little else than accidental rents in a simple frond; in _P. Nelsoni_ they are apparently _nothing_ more; and similar divisions, evidently, however, the effect of accident, and less rounded at their extremities than in at least _P. comptum_, we find exhibited by some of the Helmsdale specimens of Tæniopteris (See Fig. 142, p. 488.) But whatever the nature of these simple fronds, they seem to impart much of its peculiar character, all the world over, to the flora of the Oolitic ages.

PECOPTERIS OBTUSIFOLIA.]

PACHYPTERIS.]

The compound ferns of the formation are numerous, and at least proportionally a considerable part of them seem identical in species with those of the Oolite of England. (See Fig. 143.) Among these there occur _Pecopteris Whitbiensis_, _Pecopteris obtusifolia_, _Pecopteris insignis_,--all well marked English species; with several others. It has, besides, its apparent ferns, that seem to be new--(Fig. 144)--that are at least not figured in any of the fossil floras to which I have access,--(Fig. 145),--such as a well defined Pachypteris, with leaflets broader and rounder than the typical _P. lanceolata_, and a much stouter midrib; a minute Sphenopteris too, and what seems to be a Phlebopteris, somewhat resembling _P. propinqua_, but greatly more massive in its general proportions. The equisetacea we find represented in the Brora deposits by _Equisetum columnare_,--a plant the broken remains of which occur in great abundance, and which, as was remarked by our President many years ago, in his paper on the Sutherlandshire Oolite, must have entered largely into the composition of the bed of lignite known as the Brora Coal. We find associated with it what seems to be the last of the Calamites,--_Calamites arenaceus_,--a name, however, which seems to have been bestowed both on this Oolitic plant and a resembling Carboniferous species. The deposit has also its Lycopodites, though, from their resemblance in foliage to the conifers, there exists that difficulty in drawing the line between them to which I have already adverted. One of these, however, so exactly resembles a lycopodite of both the Virginian and Yorkshire Oolite,--_L. uncifolius_,--that I cannot avoid regarding it as specifically identical; and it seems more than doubtful whether the stem which I have placed among the conifers is not a lycopodite also. It exhibits not only the general outline of the true club moss, but, like the fossil club mosses too, it wants that degree of ligniferous body in the rock which the coniferous fossils almost always possess. Yet another of the organisms of the deposit seems to have been either a lycopodite or a fern. Its leaflets are exceedingly minute, and set alternately on a stem slender as a hair,--circumstances in which it resembles some of the tiny lycopodites of the tropics, such as _Lycopodium apodium_. I must mention, however, that the larger plant of the same beds which I have placed beside it, and which resembles it so closely that my engraver finds it difficult to indicate any other difference between them than that of size, appears to be a true fern, not a lycopodium. To yet another vegetable organism of the system,--an organism which must be regarded, if I do not mistake its character, as at once very interesting and extraordinary, occurring as it does so low in the scale, and bearing an antiquity so high,--I shall advert, after a preliminary remark on a general characteristic of the flora to which it belongs, but to which it seems to furnish a striking exception.

PHLEBOPTERIS.]

From the disappearance of many of those anomalous types of the Coal Measures which so puzzle the botanist, and the extensive introduction of types that still exist, we can better conceive of the general features and relations of the flora of the Oolite than of those of the earlier floras. And yet the general result at which we arrive may be found not without its bearing on the older vegetations also. Throughout almost all the families of this Oolitic flora, there seems to have run a curious bond of relationship, which, like those ties which bound together some of the old clans of our country, united them, high and low, into one great sept, and conferred upon them a certain wonderful unity of character and appearance. Let us assume the ferns as our central group. Though less abundant than in the earlier creation of the Carboniferous system, they seem to have occupied, judging from their remains, very considerable space in the Oolitic vegetation; and with the ferns there were associated in great abundance the two prevailing families of the Pterides,--Equiseta and Lycopodia,--plants which, in most of our modern treatises on the ferns proper, take their place as the fern allies. (See Fig. 148.) Let us place these along two of the sides of a pentagon,--the Lycopodia on the right side of the ferns, the Equiseta on the left; further, let us occupy the two remaining sides of the figure by the Coniferæ and the Cycadaceæ,--placing the Coniferæ on the side next the Lycopodia, and the Cycadaceæ, as the last added keystone of the erection, between these and the Equiseta. And now, let us consider how very curious the links are which give a wonderful unity to the whole. We still find great difficulty in distinguishing between the foliage of some of even the existing club mosses and the conifers; and the ancient Lepidodendra are very generally recognized as of a type intermediate between the two. Similar intermediate types, exemplified by extinct families, united the conifers and the ferns. The analogy of _Kirchneria_ with the _Thinnfeldia_, says Dr. Braun, is very remarkable, notwithstanding that the former is a fern, and that the latter is ranked among conifers. The points of resemblance borne by the conifers to the huge Equiseta of the Oolitic period seem to have been equally striking. The pores which traverse longitudinally the channelled grooves by which the stems of our recent Equiseta are so delicately fluted, are said considerably more to resemble the discs of pines and araucarians than ordinary stomata. Mr. Francis does not hesitate to say, in his work on British Ferns, that the relation of this special family to the Coniferæ is so strong, both in external and internal structure, that it is not without some hesitation he places them among the fern allies; and it has been ascertained by Mr. Dawes, in his researches regarding the calamite, that in its internal structure this apparent representative of Equiseta in the earlier ages of the world united "a network of quadrangular tissue similar to that of Coniferæ to other quadrangular cells arranged in perpendicular series," like the cells of plants of a humbler order. The relations of the Cycadacean order to ferns on the one hand, and to the Coniferæ on the other, are equally well marked. As in the ferns, the venation of its fronds is circinate, or scroll-like,--they have in several respects a resembling structure,--in at least one recent species they have a nearly identical form; and fronds of this fern-like type seem to have been comparatively common during the times of the Oolite. On the other hand, the Cycadaceæ manifest close relations to the conifers. Both have their seeds originally naked; both are cone-bearing; both possess discs on the sides of their cellules; and in both, in the transverse section, these cellules are subhexagonal, and radiate from a centre. Such were the very curious relations that united into one great sept the prevailing members of the Oolitic flora; and similar bonds of connection seem to have existed in the floras of the still earlier ages.

IMBRICATED STEM.

(_Helmsdale._)]

(_Helmsdale._)]

In the Oolite of Scotland I have, however, at length found trace of a vegetable organism that _seems_ to have lain, if I may so express myself, outside the pentagon, and was not a member of any of the great families which it comprised. (See Fig. 151.) I succeeded about four years ago in disinterring from the limestone of Helmsdale what _appears_ to be a true dicotyledonous leaf, with the fragment of another leaf, which I at first supposed might have belonged to a plant of the same great class, but which I now find might have been a portion of a fern. When _Phlebopteris Phillipsii_ was first detected in the Oolite of Yorkshire, Lindley and Hatton, regarding it as dicotyledonous, originated their term Dictyophillum as a general one for all such leaves. But it has since been assigned to a greatly lower order,--the ferns; and Sir Charles Lyell has kindly shown me that an exotic fern of the present day exhibits exactly such a reticulated style of venation as my Helmsdale fragment. (See Fig. 152, p. 497.) The other leaf, however, though also fragmentary, and but indifferently preserved, seems to be decidedly marked by the dicotyledonous character; and so I continue to regard it, provisionally at least, as one of the first precursors in Scotland of our great forest trees, and of so many of our flowering and fruit-bearing plants, and as apparently occupying the same relative place in advance of its contemporaries as that occupied by the conifer of the Old Red Sandstone in advance of the ferns and Lycopodaceæ with which I found it associated. In the arrangement of its larger veins the better preserved Oolitic leaf somewhat resembles that of the buckthorn; but its state of keeping is such that it has failed to leave its exterior outline in the stone.

One or two general remarks, in conclusion, on the Oolite flora of Scotland may be permitted me by the Association. In its aspect as a whole it greatly resembles the Oolite flora of Virginia, though separated in space from the locality in which the latter occurs by a distance of nearly four thousand miles. There are several species of plants common to both, such as _Equisetum columnare_, _Calamites arenaceus_, _Pecopteris Whitbiensis_, _Lycopodites uncifolius_, and apparently _Tæniopteris magnifolia_; both, too, manifest the great abundance in which they were developed of old by the beds of coal into which their remains have been converted. The coal of the Virginia Oolite has been profitably wrought for many years: it is stated by Sir Charles Lyell, who carefully examined the deposit, and has given as the results of his observation in his second series of Travels in the United States, that the annual quantity taken from the Oolitic pits by Philadelphia alone amounted to ten thousand tons; and though, on the other hand, the Sutherlandshire deposit has never been profitably wrought, it has been at least wrought more extensively than any other in the British Oolite. The seam of Brora, varying from three feet three to three feet eight inches in thickness, furnished, says Sir Roderick Murchison, between the years 1814 and 1826, no less than seventy thousand tons of coal. Such is its extent, too, that nearly thirty miles from the pit's mouth (in Ross-shire under the Northern Sutor) I have found it still existing, though in diminished proportions, as a decided coal seam, which it must have taken no small amount of vegetable matter to form. And almost on the other side of the world, nearly five thousand miles from the Sutherland beds, and more than eight thousand miles from the Carolina ones, the same Oolitic flora again appears, associated with beds of coal. At Nagpur in Central India the Oolitic Sandstones abound in simple fronded ferns, such us Tæniopteris and Glossopteris, and has its Zamites, its coniferous leaves, and its equisetaceæ.

Compared with existing floras, that of our Scottish Oolite seems to have most nearly resembled the flora of New Zealand,--a flora remarkable for the great abundance of its ferns, and its vast forests of coniferous trees, that retain at all seasons their coverings of acicular spiky leaves. It is to this flora that _Dacrydium cupressinum_,--so like a club moss in its foliage,--belongs; and _Podocarpus ferrugineus_,--a tree which more closely resembles in its foliage the Eathie conifer, save that its spiky leaves are somewhat narrower and longer than any other with which I am acquainted. About two thirds of the plants which cover the plains, or rise on the hill-sides of that country, are cryptogamic, consisting mainly of ferns and their allies; and it is a curious circumstance,--which was, however, not without precedent in the merely physical conditions of the Oolitic flora of Scotland,--that so shallow is the soil even where its greatest forests have sprung up, and so immediately does the rock lie below, that the central axes of the trees do not elongate downwards into a tap, but throw out horizontally on every side a thick network of roots, which rises so high over the surface as to render walking through the woods a difficult and very fatiguing exercise. The flora of the Oolite, like that of New Zealand, seems to have been in large part cryptogamic, consisting of ferns and the allied horse-tail and club moss families. Its forests seem to have contained only cone-bearing trees; at least among the many thousand specimens of its fossil woods which have been examined, no tissue of the true, dicotyledonous character has yet been found; and with the exception of the leaves just described, all those yet found in the System, which could have belonged to true trees, are of the acicular form common to the Coniferæ, and show in their dense ligneous structure that they were persistent, not deciduous. Nor is there evidence wanting that many of the Coniferæ of the period grew in so shallow a soil, that their tap-roots were flattened and bent backwards, and they were left to derive their sole support, like the trees of the New Zealand forests, from such of their roots as shot out horizontally. We even know the nature of the rock upon which they rested. As shown by fragments still locked up among the interstices of their petrified roots, it was an Old Red flagstone similar to that of Caithness in the neighborhood of Wick and Thurso, and containing the same fossil remains. In the water-rolled pebbles of the Conglomerate of Helmsdale and Port Gower,--pebbles encrusted by Oolitic corals, and enclosed in a calcareous paste, containing Oolitic belemnites and astreæ,--I have found the well marked fishes and fucoids of the Old Red Sandstone. As shown by the appearance of the rounded masses in which these lay, they must have presented as ancient an appearance in the times of the Lower Oolite as they do now; and the glimpse which they lent of so remote an antiquity, through the medium of an antiquity which, save for the comparison which they furnished the means of instituting, might be well deemed superlatively remote, I have felt singularly awe-inspiring and impressive. Macaulay anticipates a time when the traveller from some distant land shall take his stand on a broken arch of London Bridge to survey the ruins of St. Paul's. In disinterring from amid the antique remains of the Oolite the immensely more antique remains of the Old Red Sandstone, I have felt as such a traveller would feel if, on setting himself to dig among the scattered heaps for memorials of the ruined city, he had fallen on what had been once the Assyrian Gallery of the British Museum, and had found mingling with the antiquities of perished London the greatly older and more venerable antiquities of Nineveh or of Babylon. The land of the Oolite in this northern locality must have been covered by a soil which,--except that from a lack of the boulder clays it must have been poorer and shallower,--must have not a little resembled that of the lower plains of Cromarty, Caithness, and Eastern Ross. And on this Palæozoic platform, long exposed, as the Oolitic Conglomerates abundantly testify, to denuding and disintegrating agencies,--a platform beaten by the surf where it descended to the sea level, and washed in the interior by rivers, with here a tall hill or abrupt precipice, and there a flat plain or sluggish morass,--there grew vast forests of cone-bearing trees, tangled thickets of gigantic equisetaceæ, numerous forms of Cycas and Zamia, and wide-rolling seas of fern, amid whose open spaces club mosses of extinct tribes sent forth their long, creeping stems, spiky and dry, and thickly mottled with pseudo-spore-bearing catkins.

The curtain drops over this ancient flora of the Oolite in Scotland; and when, long after, there is a corner of the thick enveloping screen withdrawn, and we catch a partial glimpse of one of the old Tertiary forests of our country, all is new. Trees of the high dicotyledonous class, allied to the plane and the buckthorn, prevail in the landscape, intermingled, however, with dingy funereal yews; and the ferns and equisetæ that rise in the darker openings of the wood approach to the existing type. And yet, though _eons_ of the past eternity have elapsed since we looked out upon Cycas and Zamia, and the last of the Calamites, the time is still early, and long ages must lapse ere man shall arise out of the dust, to keep and to dress fields waving with the productions of yet another and different flora, and to busy himself with all the labor which he taketh under the sun. Our country, in this Tertiary time, has still its great outbursts of molten matter, that bury in fiery deluges many feet in depth, and many square miles in extent, the debris of wide tracts of woodland and marsh; and the basaltic columns still form in its great lava bed; and ever and anon, as the volcanic agencies awake, clouds of ashes darken the heavens, and cover up the landscape as if with accumulated drifts of a protracted snow storm. Who shall declare what, throughout those long ages, the history of creation has been? We see at wide intervals the mere fragments of successive floras; but know not how what seem the blank interspaces were filled, or how, as extinction overtook in succession one tribe of existences after another, and species, like individuals, yielded to the great law of death, yet other species were brought to the birth, and ushered upon the scene, and the chain of being was maintained unbroken. We see only detached bits of that green web which has covered our earth ever since the dry land first appeared; but the web itself seems to have been continuous throughout all time; though ever as breadth after breadth issued from the creative loom, the pattern has altered, and the sculpturesque and graceful forms that illustrated its first beginnings and its middle spaces have yielded to flowers of richer color and blow, and fruits of fairer shade and outline; and for gigantic club mosses stretching forth their hirsute arms, goodly trees of the Lord have expanded their great boughs; and for the barren fern and the calamite, clustering in thickets beside the waters, or spreading on flowerless hill slopes, luxuriant orchards have yielded their ruddy flush, and rich harvests their golden gleam.

THE END.

FOOTNOTES:

[1] The Prayer will be found at the end of these Memorials.

[2] The same revolver proved to be the instrument of death to another person, two days after. The circumstances are thus related in the _Edinburgh Witness_ of December 27:--

"A most melancholy event, arising out of the following circumstances, occurred yesterday in the shop of Mr. Thomson, gunmaker. In the beginning of July, last year, Mr. Hugh Miller bought a six-shot revolving chamber pistol, size of ball ninety-two to the pound, from the late firm of Messrs. Alexander Thomson & Son, gunmakers, 16 Union Place. A few days after, he called and said he thought it a little stiff in its workings, and got it made to revolve more readily. The pistol has not been seen by Mr. Thomson since then; but in his absence a few minutes at dinner yesterday, Professor Miller called about twenty minutes from two, and asked Mr. Thomson's foreman how many of the six shots had been fired. He added, 'Mind, it is loaded.' The foreman, instead of removing the breech or chamber to examine it, bad incautiously turned the pistol entire towards his own person, and lifting up the hammer with his fingers, while he counted the remaining loaded chambers, he must have slipped his fingers while the pistol was turned to his own head. It exploded, and the ball lodging in the angle of his right eye, he fell back a lifeless corpse. The pistol is a bolted one, which permits of being carried loaded with perfect safety. Having been wet internally, rust may have stopped the action of the bolt. It is a singular fact that Hugh Miller dropped the pistol into the bath, where it remained for several hours. This may account for the apparent incaution of Mr. Thomson's foreman."

[3] See _ante_, p. 9.

[4] The horizontal lines in this diagram indicate the divisions of the various geologic systems; the vertical lines the sweep of the various classes or sub-classes of plants across the geologic scale, with, so far as has yet been ascertained, the place of their first appearance in creation; while the double line of type below shows in what degree the order of their occurrence agrees with the arrangement of the botanist. The single point of difference indicated by the diagram between the order of occurrence and that of arrangement, viz., the transposition of the gymnogenous and monocotyledonous classes, must be regarded as purely provisional. It is definitely ascertained that the Lower Old Red Sandstone has its coniferous wood, but not yet definitely ascertained that it has its true monocotyledonous plants; though indications are not awanting that the latter were introduced upon the scene at least as early as the pines or araucarians; and the chance discovery of some fossil in a sufficiently good state of keeping to determine the point may, of course, at once retranspose the transposition, and bring into complete correspondence the geologic and botanic arrangements.