Chapter 5

Scotland has its four fossil floras,--its flora of the Old Red Sandstone, its Carboniferous flora, its Oolitic flora, and that flora of apparently Tertiary age of which his Grace the Duke of Argyll found so interesting a fragment overflown by the thick basalt beds and trap tuffs of Mull. Of these, the only one adequately known to the geologist is the gorgeous flora of the Coal Measures,--probably the richest, in at least individual plants, which the world has yet seen. The others are all but wholly unknown; and the Association may be the more disposed to tolerate the comparative meagreness of the few brief remarks which I purpose making on two of their number,--the floras of the Old Red Sandstone and the Oolite,--from the consideration that that meagreness is only too truly representative of the present state of our knowledge regarding them; and that if my descriptions be scanty and inadequate, it is only because the facts are still few. How much of the lost may yet be recovered I know not; but the circumstance that two great floras,--remote predecessors of the existing one,--which once covered with their continuous mantle of green the dry land of what is now Scotland, should be represented by but a few coniferous fossils, a few cycadaceous fronds, a few ferns and club mosses, must serve to show what mere fragments of the past history of our country we have yet been able to recover from the rocks, and how very much in the work of exploration and discovery still remains for us to do. We stand on the further edge of the great floras of by-past creations, and have gathered but a few handfuls of faded leaves, a few broken branches, a few decayed cones.

The Silurian deposits of our country have not yet furnished us with any unequivocal traces of a terrestrial vegetation. Professor Nicol of Aberdeen, on subjecting to the microscope the ashes of a Silurian anthracite which occurs in Peeblesshire, detected in it minute tubular fibres, which seem, he says, to indicate a higher class of vegetation than the algae; but these may have belonged to a marine vegetation notwithstanding. I detected some years ago, in the Trilobite-bearing schists of Girvan, associated with graptolites of the Lower Silurian type, a vegetable organism somewhat resembling the leaf of one of the pond weeds,--an order of plants, some of whose species, such as Zostera, find their proper habitats in salt water. I have placed beside this specimen a fragment of the same graptolite-bearing rock, across which I have pasted part of a leaf of _Zostera marina_, the only plant of our Scottish seas which is furnished with true roots, bears real flowers inclosed in herbaceous spathes, and produces a well formed farinaceous seed. It will be seen, that in the few points of comparison which can be instituted between forms so exceedingly simple, the ancient very closely resembles the recent organism. It is not impossible, therefore, that the Silurian vegetable may have belonged to some tribe of plants allied to Zostera; and if so, we can easily conceive how the Silurian anthracite of our country may be altogether of marine origin, and may yet exhibit in its microscopic tubular fibres vestiges of a vegetation higher than the algae.

[It were well, in dealing with the very ancient floras, in which equivocal forms occur that might have belonged to either the land or the sea, to keep in view those curious plants of the present time, the habitats of which are decidedly marine, but which are marked by many of the peculiarities of the seed-bearing plants of the land. The superiority of Zostera to the common sea weeds of our coasts appears to have struck in the north of Scotland eyes very little practised in such matters, and seems to have given rise, in consequence, to a popular myth. _Zostera marina_ abounds on a series of sand banks, partially uncovered by the larger stream tides, which lie directly opposite the town of Cromarty, near the spot pointed out by tradition as the site of an earlier town, which was swept away some two or three hundred years ago by the encroachments of the sea. And these banks, with their thick covering of green Zostera, used to be pointed out by the fishermen of the place, in my younger days, as the _meadows_ of the old town, still bearing their original coverings of vegetation,--a vegetation altered no doubt by the "sea change" that had come over it, but still essentially the same, it was said, as that which had smiled around the old burgh, and not at all akin to the brown kelp or tangle that every storm from the boisterous north-east heaps along the shore. It was virtually affirmed that the luxuriant terrestrial grasses of ancient Cromarty had made a virtue of necessity in their altered circumstances; and that, settling down into grasses of the sea, they remained to testify that an ancient Cromarty there had _once been_. _Zostera marina_, like most plants of the land, ripens its seeds towards the close of autumn; and I have seen a smart night's frost at this season, when coincident with a stream tide that laid bare the beds, nip its seed-bearing stems by thousands; and have found them strewed along the beach a few days after, with all their grass-like spikes fully developed, and their grain-like seeds charged with a farinaceous substance, which one would scarce expect to find developed in the sea. In the higher reaches of the Cromarty Firth, the Zostera beds, which are of great extent, are much frequented, during the more protracted frosts of a severe winter, by wild geese and swans, that dig up and feed upon the saccharine roots of the plant. The Zostera of the warmer latitudes attain to a larger size than those of our Scottish seas. "A southern species," says Loudon, "_Zostera oceanica_, has leaves a foot long and an inch broad. It is used as a thatch, which is said to last a century; bleaches white with exposure; and furnishes the rush-like material from which the envelops of Italian liquor flasks are prepared." The simple rectilinear venation of ribbon-like fronds, usually much broken, that occurs in the Lower Old Red Sandstone, has often reminded me of that exhibited by this exotic species of Zostera.]

Associated with the earliest ichthyic remains of the Old Red Sandstone, we find vegetable organisms in such abundance, that they communicate often a fissile character to the stone in which they occur. But, existing as mere carbonaceous markings, their state of keeping is usually so bad, that they tell us little else than that the antiquely-formed fishes of this remote period swam over sea bottoms darkened by forests of algae. The prevailing plant was one furnished with a long, smooth stem, which, though it threw off, in the alternate order, numerous branches at least half as stout as itself, preserved its thickness for considerable distances without diminution,--a common fucoidal characteristic. We find its remains mixed in the rock, though sparingly, with those of a rough-edged plant, knobbed somewhat like the thong-like receptacles of _Himanthalia lorea_, which also threw off branches like the other, but diminished more rapidly. A greatly more minute vegetable organism of the same beds, characterized by its bifid partings, which strike off at angles of about sixty, somewhat resembles the small-fronded variety of _Dictyota dichotoma_, save that the slim terminations of the frond are usually bent into little hooks, like the tendrils of the pea just as their points begin to turn. Another rather rare plant of the period, existing as a broad, irregularly cleft frond, somewhat resembling that of a modern _Cutleria_ or _Nitophyllum_, betrays at once, in its outline and general appearance, its marine origin; as does also an equally rare contemporary, which, judging from its appearance, seems to have been a true fucus. It exists in the rock as if simply drawn in Indian ink; for it exhibits no structure, though, as in some of the ferns of the Coal Measures, what were once the curls of its leaflets continue to exist as sensible hollows on the surface. It broadens and divides atop into three or four lobes, and these, in turn, broaden and divide into minor lobes, double or ternate, and usually rounded at their terminations. In general appearance the plant not a little resembles those specimens of _Fucus vesiculosus_ which we find existing in a diminutive form, and divested of both the receptacles and the air vessels, at the mouth of rivers. Of two other kinds of plants I have seen only confused masses, in which the individuals were so crowded together, and withal so fragmentary and broken, that their separate forms could not be traced. In the one the general appearance was such as might be produced by compressed and tangled masses of _Chorda filium_, in which the linear and even tubular character of the plant could be determined, but not its continuous, cord-like aspect; in the other, the fragments seemed well nigh as slim as hairs, and the appearance was such as might be produced by branches of that common ectocarpus, _E. littoralis_, which may be seen on our rocky coasts roughening at low water the stems of laminaria. When highly magnified, a mesial groove might be detected running along each of the hair-like lines. With these marine plants we occasionally find large rectilinear stems, resolved into a true coal, but retaining no organic character by which to distinguish them. As I have seen some of these more than three inches in diameter, and, though existing as mere fragments, several feet in length, they must, if they were also plants of the sea, have exceeded in size our largest laminaria.[46] And such are the few vegetable organisms, of apparently aquatic origin, which I have hitherto succeeded in detecting in the Lower Old Red Sandstone of Scotland.[47] Their individual numbers, however, must have been very great, though, from the destructible character of their tissues, their forms have perished in the stone. The immensely developed flagstones of Caithness seem to owe their dark color to organic matter mainly of vegetable origin. So strongly bituminous, indeed, are some of the beds of dingier tint, that they flame in the fire like slates steeped in oil.

The remains of a terrestrial vegetation in this deposit are greatly scantier than those of its marine plants; but they must be regarded as possessing a peculiar interest, as, with the exception of the spore cases of the Ludlow rocks, the oldest of their class, in at least the British islands, whose true place in the scale can be satisfactorily established. In the flagstones of Orkney there occurs, though very rarely, a minute vegetable organism, which I have elsewhere described as having much the appearance of one of our smaller ferns, such as the maidenhair-spleenwort, or dwarf moonwort. It consists of a minute stem, partially covered by what seems to be a small sheath or hollow bract, and bifurcates into two fronds or pinnae, fringed by from ten to twelve leaflets, that nearly impinge on each other, and somewhat resemble in their mode of arrangement the leaflets of one of our commonest Aspleniums,--_Asplenium trichomanes_. One of our highest authorities, however, in such matters (Professor Balfour of Edinburgh) questions whether this organism be in reality a fern, and describes it from the specimen on the table, in the Palaeontological chapter of his admirable Class Book, simply as "a remarkable pinnate frond." (Fig. 13, p. 56.) We find it associated with the remains of a terrestrial plant allied to lepidodendron, and which in size and general appearance not a little resembles one of our commonest club mosses,--_Lycopodium clavatum_.[48] It sends out its branches in exactly the same style,--some short and simple, others branched like the parent stem,--in an arrangement approximately alternate; and is everywhere covered, stem and branch, by thickly set scale-like leaflets, that, suddenly narrowing, terminate in exceedingly slim points. It has, however, proportionally a stouter stem than Lycopodium; its leaves, when seen in profile, seem more rectilinear and thin; and none of its branches yet found bear the fructiferous stalk or spike. Its resemblance, however, to this commonest of the Lycopodia,--a plant that may be gathered by handfuls on the moors by which the flagstones are covered,--is close enough to suggest a new reading of the familiar adage on the meeting of extremes. Between the times of this ancient fossil,--one of the oldest of land plants yet known,--and those of the existing club moss that now scatters its light spores by millions over the dead and blackened remains of its remote predecessor, many creations must have intervened, and many a prodigy of the vegetable world appeared, especially in the earlier and middle periods,--Sigillaria, Favularia, Knorria, and Ulodendron,--that have had no representatives in the floras of latter times; and yet here, flanking the immense scale at both its ends, do we find plants of so nearly the same form and type, that it demands a careful survey to distinguish their points of difference. Here, for instance, to illustrate the fact, is there a specimen of _Lycopodium clavatum_, from one of these Caithness moors, that agrees branch for branch, and both in the disposition of its scales and in general outline, with the specimen in the stone. What seems to be an early representative of the Calamites occurs in the same beds. Some of the specimens are of large size,--at least from nine inches to a foot in circumference,--and retain their thickness, though existing as fragments several feet in length, with but little diminution throughout. They resembled the interior casts of Calamites in being longitudinally furrowed; but the furrows are flatter, and are themselves minutely striated lengthwise by lines as fine as hairs; and, instead of presenting any appearance of joints, there run diagonally across the stems, interrupted and very irregular lines of knobs. These I find referred to by Dr. Joseph Hooker, in describing a set of massive but ill preserved remains of the same organism detected in South Ness quarry, near Lerwick, by the Hon. Mr. Tuffnell, as taking, in two of the specimens, "the appearance of transverse knobs and bars (mayhap spirally arranged) that cross the striae obliquely. But though the knobs," he adds, "may perhaps indicate a peculiar character of the plants, they have more probably been caused by pressure during silicification." As, however, they also occur in the best preserved fragment of the plant which I have yet seen,--a Thurso specimen which I owe to my friend Mr. Dick,--I deem it best to regard them, provisionally at least, as one of the characteristics of the plant. I may mention, that while I disinterred one of my specimens from the Thurso flagstones, where it occurred among remains of Dipterus and Asterolepis, I derived another specimen from the great overlying formation of pale Red Sandstone to which the lofty hills of Hoy and the tall mural precipices of Dunnet Head belong; and that this plant is the only organism which has yet been found in this uppermost member of the Lower Old Red, to at least the north of the Moray Firth. Another apparently terrestrial organism of the lower formation, of, however, rare occurrence, very much resembles a sheathing bract or spathe. It is of considerable size,--from four to six inches in length, by from two to three inches in breadth,--of a broadly elliptical and yet somewhat lanceolate form, deeply but irregularly corrugated, the rugae exhibiting a tendency to converge towards both its lower and upper terminations, and with, in some instances, what seems to be the fragment of a second spathe springing from its base. Another and much smaller vegetable organism of the same beds presents the form of a spathe-enveloped bud or unblown flower wrapped up in its calyx; but all the specimens which I have yet seen are too obscure to admit of certain determination. I may here mention, that curious markings, which have been regarded as impressions made by vegetables that had themselves disappeared, have been detected during the last twelvemonth in a quarry of the Lower Old Red Sandstone near Huntly, by the Rev. Mr. Mackay of Rhynie. They are very curious and very puzzling; but though some of the specimens present the appearance of a continuous midrib, that throws off, with a certain degree of regularity, apparent leaflets, I am inclined to regard them rather as lying within the province of the ichnologist than of the fossil botanist. They bear the same sort of resemblance to a long, thickly-leaved frond, like that of the "hard fern," that the cast of a many-legged annelid does to a club moss; and I was struck, on my first walk along the Portobello beach, after examining a specimen kindly sent me by Mr. Mackay, to see how nearly the tract of a small shore crab (_Carcinus Maenas_) along the wet sand resembled them, in exhibiting what seemed to be an obscure midrib fringed with leaflets.

But the genuine vegetable organism of the formation, indicative of the highest rank of any yet found in it, is a true wood of the cone-bearing order. I laid open the nodule which contains this specimen, in one of the ichthyolite beds of Cromarty, rather more than eighteen years ago; but though I described it, in the first edition of my little work on the Old Red Sandstone, in 1841, as exhibiting the woody fibre, it was not until 1845 that, with the assistance of the optical lapidary, I subjected its structure to the test of the microscope. It turned out, as I had anticipated, to be the portion of a tree; and on my submitting the prepared specimen to one of our highest authorities,--the late Mr. William Nicol,--he at once decided that the "reticulated texture of the transverse section, though somewhat compressed, clearly indicated a coniferous origin." I may add, that this most ancient of Scottish lignites presents several peculiarities of structure. Like some of the Araucarians of the warmer latitudes, it exhibits no lines of yearly growth; its medullary rays are slender, and comparatively inconspicuous; and the discs which mottle the sides of its sap-chambers, when viewed in the longitudinal section, are exceedingly minute, and are ranged, so far as can be judged in their imperfect state of keeping, in the alternate order peculiar to the Araucarians. On what perished land of the early Palaeozoic ages did this venerably antique tree cast root and flourish, when the extinct genera Pterichthys and Coccosteus were enjoying life by millions in the surrounding seas, long ere the flora or fauna of the Coal Measures had begun to be?

I may be here permitted to mention, that in a little volume, written in reply to a widely known and very ingenious work on the Development hypothesis, I described and figured this unequivocally genuine lignite, in order to show that a true wood takes its place among the earliest terrestrial plants known to the geologist. I at the same time mentioned,--desirous, of course, that the facts of the question should be fairly stated, whatever their bearing,--that the nodule in which it occurred had been partially washed out of the fish bed in which I found it, by the action of the surf; and my opponent, fixing on the circumstance, insinuated, in the answer with which he honored me, that it had _not_ belonged to the bed at all, but had been derived from some other formation of later date. He ought, however, to have taken into account my further statement, namely, that the same nodule which enclosed the lignite contained part of another fossil, the well marked scales of _Diplacanthus striatus_, an ichthyolite restricted, like the Coccosteus (a specimen of which occurred in a neighboring nodule), to the Lower Old Red Sandstone exclusively. If there be any value whatever in palaeontological evidence, this Cromarty lignite must have been deposited in a sea inhabited by the Coccosteus and Diplacanthus. It is demonstrable that, while yet in the recent state, a Diplacanthus lay down and died beside it; and the evidence in the case is unequivocally this, that in the oldest portion of the oldest terrestrial flora yet known, there occurs the fragment of a tree quite as high in the scale as the stately Norfolk Island pine, or the noble cedar of Lebanon.

[I have failed hitherto in finding any remains of terrestrial plant-covered surfaces in the Old Red Sandstone of Scotland, though decided traces of desiccated sub-aerial ones are not rare. Shallows and banks seem to have been numerous during the period of at least the Lower formation. The flagstones of Caithness and Orkney, and the argillaceous fish beds of Cromarty and Ross, not only abound in the ripple-marked surfaces of a shallow sea, but also in cracked and flawed planes that must have dried and split into polygonal partings in the air and the sun. The appearance of these in the neighborhood of the town of Thurso, about half a mile to the east of the river, is not a little curious. Bearing throughout the general dingy hue of the flagstones, they yet consist of alternating beds of two distinct characters and qualities. The one kind, fissile, finely grained, and sharply ripple-marked, seems to have been deposited in shallow water; the other, not fissile, but, if I may so speak, felted together so as to yield with difficulty to the hammer in any direction, and traversed by polygonal partings, filled up usually by the substance of the overlying stratum, appears to have had a different origin. The state of keeping, too, in which the ichthyic remains of these alternating beds occur is always very different. The smaller and more delicately organized fishes are never found entire, save in the fissile, finely grained beds; in the others we detect only scattered fragments; and even these, unless they belonged to the robust Asterolepis or his congeners,--which, however, in these beds they usually do,--much broken. The polygonal partings seem to indicate that these toughly-felted beds, whose very style of weathering--rough, gnarled, fretted into globose protuberances and irregular hollows--shows that it had not been formed by quiet deposition, must have had their broad backs raised for a time above the surface of the water, to be desiccated in the hot sun. And the fragmentary state of the fossils which they contain seems to point, with the roughnesses of their weathered surfaces, to some peculiarity in their origin. The recollection which they awoke in my mind with each visit I paid them for three years together, may probably indicate what that origin was. I had a relation who died more than a quarter of a century ago, who passed many years in British Guiana, in the colony of Berbice, and whose graphic descriptions of that part of South America made a strong impression upon me when a boy, and still dwells in my memory. He was settled on a cotton plantation near the coast side; and so exceedingly flat was the surrounding country, that the house in which he dwelt, though nearly two miles distant from the shore, stood little more than five feet above its level. The soil consisted of a dark gray consolidated mud; and in looking seawards from the margin of the land, there was nothing to be seen, when the tide fell, save dreary mud flats whole miles in extent, with the line of blue water beyond stretching along the distant horizon. These mud flats were much frequented by birds of the wader family, that used to come and fish in the shallow pools for the small fry that had lingered behind when the tide fell; and my cousin, a keen sportsman in his day, has told me that he used to steal upon them in his mud shoes,--flat boards attached to the soles, like the snow shoes of the higher latitudes,--and enjoy rare sport in knocking down magnificent game, such as "the roseate spoonbill" and "gorgeous flamingo." There were times, however, when the mud shoe proved of no avail, and the flat expanse remained impassable for weeks,--

"A boggy syrtis, neither sea Nor good dry land."

The coast,--directly impinged on by the drift current, and beaten by the long roll of waves which had first begun to rise under the impulsions of the trade winds on the African coast two thousand miles away,--was much exposed to tempests; and after every fresh storm from the east, a huge bank of mud used to come rolling in from the sea, three or four feet abreast, and remain wholly impassable until, during some two or three neap tides, its surface had been exposed to a tropical sun, and partially consolidated by the heat. And then the waste would become passable as before, and the chopped and broken surface, exposed to the ordinary action of the sea, and to gradual depositions during flood, would begin to be smoothed over, and the birds would find themselves no longer safe. Now, I am inclined to think that we have here the conditions necessary to the formation of the Thurso deposits. Let us suppose, near where Thurso now stands, a wide tract of flat mud banks in a sea so shallow as to be laid dry at ebb for miles together. Let us further suppose periods of tranquil deposition or re-arrangement, during which one ripple-marked stratum is laid quietly down over another, and the fish, killed by accident, or left stranded by the evaporation of the little pools, are covered up, like the plants in a botanist's drying-book, in a state of complete entireness. Let us yet further suppose great mud banks driven by occasional tempests from the deeper water beyond, and so heaped up over these sedimentary beds as to be exposed during even the flood of neap tides to the desiccating influences of the atmosphere and the sun, until the surface has become hard as a sun-burned brick, and has chopped into polygonal partings, with wide rents between. And finally, let us suppose the whole in this state laid under water at the return of stream tides, and exposed to the ordinary sedimentary action. Does it not seem probable that the alternating beds in all their conditions would be given us by such a process? In the stratum represented by the mud bank, the stone would be of what I have termed a _felted_, not a fissile character; its organic remains would exist in a fragmentary and scattered state,--for, torn up from their places of original deposition, and rolled onwards in the storm-impelled mud, they could not fail to be broken up and dispersed; and further, they would be in large part those of bulky deep-sea fishes. And lastly, the surface of these beds would be polygonally cracked and flawed, and the wider cracks filled up by the substance of the overlying strata. And these overlying strata, on the other hand,--the result of a period of quiet deposition in shallow water,--would be regularly bedded, and their ichthyic remains, consisting mainly of small littoral fishes, would be preserved in a state of comparative entireness. For, however, such numerous repetitions of alternately _felted_ and fissile ripple-marked strata as we find in the neighborhood of Thurso,--repetitions carried on for hundreds of feet in vertical extent,--we require yet another condition,--that condition of gradual subsidence in the general crust which can alone account for the fact so often pressed upon the geologist in exploring the Coal Measures, that in deposits thousands of feet in thickness, each stratum in succession had been laid down in a shallow sea.]

It is a curious circumstance, that the Old Red flagstones which lie along the southern flanks of the Grampians, and are represented by the gray stone known in commerce as the Arbroath Pavement, have not, so far as is yet known, an organism in common with the Old Red flagstones of the north. I at one time supposed that the rectilinear, smooth-stemmed fucoid, already described, occurred in both series, as the gray stones have also their smooth-stemmed, rectilinear, tape-like organism; but the points of resemblance were too few and simple to justify the conclusion that they were identical, and I have since ascertained that they were entirely different plants. The fucoid of the Caithness flagstones threw off, as I have shown, in the alternate order, numerous ribbon-like branches or fronds; whereas the ribbon-like fronds or branches of the Forfarshire plant rose by dozens from a common root, like the fronds of Zostera, and somewhat resembled a scourge of cords fastened to a handle. Contemporary with this organism of the gray flagstone formation, and thickly occupying the planes on which it rests, there occur fragments of twisted stems, some of them from three to four inches in diameter (though represented by but mere films of carbonaceous matter), and irregularly streaked, or rather _wrinkled_, longitudinally, like the bark of some of our forest trees, though on a smaller scale. With these we find in considerable abundance irregularly-shaped patches, also of carbonaceous matter, reticulated into the semblance of polygonal, or, in some instances, egg-shaped meshes, and which remind one of pieces of ill woven lace. When first laid open, these meshes are filled each with a carbonaceous speck; and, from their supposed resemblance, in the aggregated form, to the eggs of the frog in their albuminous envelop, the quarriers term them "puddock [frog] spawn." The slabs in which they occur, thickly covered over with their vegetable impressions, did certainly remind me, when I first examined them some fifteen years ago, of the bottom of some stagnant ditch beside some decaying hedge, as it appears in middle spring, when paved with fragments of dead branches and withered grass, and mottled with its life-impregnated patches of the gelid substance regarding which a provincial poet tells his readers, in classical Scotch, that

"Puddock-spue is fu' o' e'en, An' every e'e 's a pu-head."[49]

Higher authorities than the quarriers,--among the rest, the late Dr. Mantell,--have been disposed to regard these polygonal markings as the fossilized spawn of ancient Batrachians; but there now seems to be evidence enough from which to conclude that they are the remains, not of the eggs of an animal, but of the seed of a plant. Such was the view taken many years ago by Dr. Fleming,--the original discoverer, let me add, of fossils both in those Upper and Middle Old Red Sandstone deposits that lie in Scotland to the south of the Grampians. "These organisms," we find him saying, in a paper published in "Cheek's Edinburgh Journal" (1831), "occur in the form of circular flat patches, not equalling an inch in diameter, and composed of numerous smaller contiguous pieces. They are not unlike what might be expected to result from a compressed berry, such as the bramble or the rasp. As, however, they are found adjacent to the narrow leaves of gramineous [looking] vegetables, and chiefly in clay slate, originally lacustrine silt, it is probable that they constituted the conglobate panicles of extinct species of the genus Junicus or Sparzanium." From specimens subsequently found by Dr. Fleming, and on which he has erected his species _Parka decipiens_, it seems evident that the nearly circular bodies (which in all the better preserved instances circumscribe the small polygonal ones) were set in receptacles somewhat resembling the receptacle or calyx of the strawberry or rasp. Judging from one of the specimens, this calyx appears to have consisted of five pieces, which united in a central stem, and were traversed by broad irregularly diverging striae. And the spawn-like patches of Carmylie appear to be simply ill preserved specimens of this fruit, whatever its true character, in which the minute circular portions, divested of the receptacle and stem, had been thrown into irregular forms by the joint agency of pressure and decay. The great abundance of these organisms,--for so abundant are they, that visitors to the Carmylie quarries find they can carry away with them as many specimens as they please,--may be regarded as of itself indicative of a vegetable origin.[50] It is not in the least strange, however, that they should have been taken for patches of spawn. The large-grained spawn of fishes, such as the lump-fish, salmon, or sturgeon, might be readily enough mistaken, in even the recent state, for the detached spherical-seed vessels of fruit, such as the bramble-berry, the stone-bramble, or the rasp. "Hang it!" I once heard a countryman exclaim, on helping himself at table to a spoonful of Caviare, which he had mistaken for a sweet-meat, and instantly, according to Milton, "with sputtering noise rejected,"--"Hang it for nasty stuff!--I took it for bramble berry jam."

Along with these curious remains Dr. Fleming found an organism which in form somewhat resembles the spike of one of the grasses, save that the better preserved bracts terminate in fan or kidney-shaped leaflets, with a simple venation radiating from the base. It is probably a fern, more minute in its pinnules than even our smallest specimens of true maidenhair. Its stipes, however, seems proportionally stouter than that of any of the smaller ferns with which I am acquainted. But the state of keeping of the specimen is not good, nor do I know that another has yet been found. Further, in the same beds Dr. Fleming found a curious nondescript vegetable, or rather part of a vegetable, with smooth narrow stems, resembling those of the smooth-stemmed organism of the Caithness flagstones, but unlike it in the circumstance that its detached nearly parallel stalks anastomose with each other by means of cross branches, that unite them in the middle, somewhat in the style of the Siamese twins. I have heard the doctor suggest, but know not whether he has placed the remark on record, that these parallel stems may have been but the internal fibres of some larger plant, whose more succulent portions have disappeared; and certainly, while such instances of anastomosis are rare among the _stems_ of plants, they are common enough among their _internal fibres_, as all who have examined the macerated _debris_ of a kitchen-garden or a turnip-field must have had occasion to remark. We sometimes, however, find cases of anastomosis among the stems of even the higher plants. I have seen oftener than once, in neglected hawthorn hedges, the branch of one plant entering into the stem of another, and becoming incorporated with its substance; and we are told by Professor Balfour, that this kind of chance adhesion is often seen in the branches of the ivy; and that not unfrequently, by a similar process, the roots of contiguous trees are united. Nor does it seem improbable, that what occasionally takes place among the higher plants of the present time may have been common among some of the comparatively low plants of so ancient a period as that of the Middle Old Red Sandstone. This formation of the gray tilestones has furnished one vegetable organism apparently higher in the scale than those just described, in a well marked Lepidodendron, which exhibits, like the Araucarian of the Lower Old Red, though less distinctly, the internal structure. It was found about sixteen years ago in a pavement quarry near Clockbriggs,--the last station on the Aberdeen and Forfar Railway as the traveller approaches the town of Forfar from the north. I owe my specimen of this ancient Lepidodendron to Mr. William Miller, banker, Dundee, an accomplished geologist, who has taken no little trouble in determining its true history. He has ascertained that it occurred deep in the rock, seventy-one feet from the surface; that the beds which rested over it were composed, in the descending order, first, of a conglomerate thirty feet thick; secondly, of a red rock four feet thick; thirdly, of twenty-eight feet of the soft shaly substance known to the quarriers as caulm; and fourthly, of more than nine feet of gray pavement, immediately under which, in a soft, argillaceous stratum, lay the organism. It was about four feet in length, bulged out at the lower end into a bulb-like protuberance, which may have been, however, merely an accidental result of its state of keeping; and threw off, at an acute angle, two branches about a foot from the top. It was covered with a bark of brittle coal, which is, however, wanting in all the fragments that have been preserved; and was resolved internally into a brown calcareous substance of about the hardness of ordinary marble, and very much resembling that into which the petrifactive agencies have consolidated the fossil trees of Granton and Craigleith. From the decorticated condition of the surviving fragments, and the imperfect preservation of the interior structure, in all save the central portions of its transverse sections, it yields no specific marks by which to distinguish it; but enough remains in its irregular network of cells, devoid of linear arrangement, and untraversed by medullary rays, to demonstrate its generic standing as a Lepidodendron.

[It has been questioned whether the lower place in the Old Red System should be assigned to the flagstones of Caithness and Ross, with their characteristic Dipterus and Coccosteus beds, or to the gray tilestones of Forfar and Kincardineshires, with their equally characteristic Cephalaspis. The evidence on the point is certainly not so conclusive as I deemed it fifteen years ago, when our highest authority on the subject not only regarded the tilestone of the Silurian regions of England as a member of the Old Red Sandstone (an arrangement which I am still disposed to deem the true one), but also held further, that there had been detected in this formation near Downtown Castle, Herefordshire, broken remains of _Dipterus macrolepidotus_, one of the best marked ichthyolites of the flagstones of Caithness and Orkney. A great and unbroken series of fossiliferous rocks, with Dipterus at its base, Cephalaspis in its medial spaces, and Holoptychius at its top, might well be regarded as the analogue of the Old Red of Scotland, with the Caithness flagstones ranged at its bottom, the Cephalaspis beds of Forfarshire placed in its middle, and the Holoptychius beds of Scot-Crag and Clashbinnie on its upper horizon; but since that time the tilestones have been transferred to the Upper Silurian division of rocks, and the evidence furnished by their supposed Dipterus has not been confirmed. And as the Old Red Sandstones of Scotland have no true fossiliferous base, but rest on primary rocks both to the south and north of the Grampians, it may be regarded as in some degree a moot point whether the lowest fossiliferous beds to the north be older or newer than those to the south, or, what is quite possible, of the same age. Provisionally, however, I have arranged my paper on the supposition that the Coccostean formation of the north is the lowest and oldest of the three; and this from the following considerations. In the first place, the Coccosteus and its contemporaries appear in the north at a very short distance above the base of the system. I have disinterred an Osteolepis from a fish bed near Cromarty only thirty-three feet over the great conglomerate, and only a hundred and twenty-nine feet over the granitic gneiss beneath; whereas the Cephalaspis beds occur high above the primary base of the system in the south,--at some distance over even the thick conglomerate of Stonehaven and Dunnottar; and under this conglomerate, as shown in the section furnished by the valley of the North Esk, there lies a pale red sandstone member of the system, estimated by Colonel Imrie at seven hundred and eighty feet in thickness. The conglomerate itself he estimates at twelve hundred feet. Adopting as correct Colonel Imrie's section, taken along the banks of the North Esk,--and the colonel was unquestionably a truthful observer,--the Cephalaspis beds of the south lie nearly two thousand (nineteen hundred and eighty) feet above the Azoic slates on which the Old Red Sandstone of Forfarshire rests, whereas the Coccosteus and Osteolepis beds of the north lie only one hundred and twenty-nine feet over the Azoic gneiss on which the Old Red Sandstone of Cromarty rests. There is thus at least _room_ in the south for an underlying fossiliferous formation between that of the Cephalaspis and the base of the system, but none in the north beneath that of the Coccosteus and its base. In the north we find the _room_ lying above, between the Coccostean and Holoptychian formations, and represented by that great unfossiliferous deposit of pale sandstone to which the hills of Hoy and the rocks of Duncansbay Head and of Tarbet Ness belong. Further, in the second place, while the upper or Holoptychian formation is found _directly_ overlying that of the Coccosteus in only one locality,--Moray,--we find it directly overlying that of the Cephalaspis in _two_ widely separated localities;--in the vast band of Old Red which runs diagonally across the island from sea to sea, parallel to the Grampian chain, and in the immensely developed Red Sandstones of England and Wales. And it is of course more probable that the two corroborative instances should represent the natural succession of the formations, and the single instance the accidental gap in the scale consequent on the missing formation, than that, _vice versa_, the solitary instance should represent the natural succession, while the two mutually corroborative ones should represent, in localities widely apart, the mere accident of the gap. But, in the third place, I attach more weight to a conclusion founded on the positive character of the groups of organic remains by which the three great formations of the Old Red System are characterized, than I do to either of these considerations. The organisms of the Cephalaspian deposits differ _generically_, and in their whole aspect, from both those of the Coccostean and Holoptychian formations; whereas the organisms of the Coccostean formations, while they resemble generically and in the group those of the Holoptychian one, mainly differ from them _specifically_. The extreme _generic_ difference in the one case argues evidently a great difference in _condition_,--the lesser specific difference in the other, a great difference in point _of time_. The Cephalaspian formation might, as a fresh water formation, be nearly contemporary with either of the other two, or, as seems more probable, interposed between them; while they themselves, on the other hand, generically similar and decidedly marine in their character, must have been so widely separated in time, that all the species of the lower group became extinct ere those of the upper one had been ushered into being. And such are some of the considerations that still lead me, notwithstanding the failure of previous evidence, to hold, at least, provisionally, that our Scottish flagstones to the north of the Grampians occupy a lower horizon than our Scottish tilestones to the south. It must, however, be stated, on the other hand, that the crustaceans of the gray tilestones of Forfar and Kincardine not a little resemble those of the Upper Silurian and red tilestone beds of England; and that, judging from the ichthyodorulites found in both, their fishes must have been at least generically allied. The crustaceans of the upper Silurian of Lesmahagow, too, seem certainly much akin to those of the Forfarshire tilestones.]

Above this gray tilestone formation lies the Upper Old Red Sandstone, with its peculiar group of ichthyic organisms, none of which seem specially identical with those of either the Caithness or the Forfarshire beds. For it is an interesting circumstance, suggestive surely of the vast periods which must have elapsed during its deposition, that the great Old Red System has, as I have just said, its three distinct platforms of organic existence, each wholly different from the others. Generically and in the group, however, the Upper fishes much more closely resemble, I repeat, the fishes of the Lower or Caithness and Cromarty platform, than they do those of the Forfarshire and Kincardine one. The vegetable remains of the Upper formation in Scotland are both rare and ill preserved. I have seen what I deemed fucoidal markings dimly impressed on the planes of some of the strata, not in the carbonaceous form so common in the other two formations, but as mere colored films of a deeper red than the surrounding matrix. Further, I have detected in the same beds, and existing in the same state, fragments of a striated organism, which may have formed part of either a true calamite, like those of the Coal Measures, or of some such striated but jointless vegetable as that of the Lower Old Red of Thurso and Lerwick.[51] With these markings ferns are occasionally found; and to one of these, from the light which it throws on the true place in the scale of a series of deposits in a sister country, there attaches no little interest. I owe my specimen to Mr. John Stewart of Edinburgh, who laid it open in a micaceous red sandstone in the quarry of Prestonhaugh, near Dunse, where it is associated with some of the better known ichthyic organisms of the Upper Old Red Sandstone, such as _Pterichthys major_ and _Holoptychius Nobilissimus_. Existing as but a deep red film in the rock, with a tolerably well defined outline, but without trace of the characteristic venation on which the fossil botanist, in dealing with the ferns, founds his generic distinctions, I could only determine that it was either a Cyclopterus or Neuropterus. My collection was visited, however, by the late lamented Edward Forbes, only a few weeks before his death; and he at once recognized in my Berwickshire fern, so unequivocally an organism of the Upper Old Red, the _Cyclopterus Hibernicus_ of those largely developed beds of yellow sandstone which form so marked a feature in the geology of the south of Ireland, and whose true place, whether as Upper Old Red or Lower Carboniferous, has been the subject of so much controversy. I had been previously introduced by Professor Forbes, in the Museum of Economic Geology in Jermyn Street, London, to an interesting collection of plants from these yellow beds, and had an opportunity afforded me of examining the only ichthyic organism hitherto found associated with them; and was struck, though I could not identify its species, with its peculiarly Old Red aspect; but the evidence of the Cyclopterus is of course more conclusive than that of the fish; and we may, I think, legitimately conclude, that in Ireland, as in our own country, it was a contemporary of the great Pterichthys (_P. major_),--the hugest, and at least one of the last, of his race,--and gave its rich green to the hill sides of what is still the Emerald Island during the latter ages of the Old Red Sandstone, and ere the Carboniferous period had yet begun. The _Cyclopterus Hibernicus_, as shown both by the Prestonhaugh specimen and those of Ireland, was a bipinnate fern of very considerable size,--probably a tree fern. Its pinnae, opposite in the lower part of the frond, are alternate in the upper; while its leaflets, which are of a sub-rhomboidal form, and so closely ranged as to impinge on each other, are at least generally alternate in their arrangement throughout. Among living plants it seems most nearly represented by a South American species,--_Didymocloena pulcherrima_,--one of the smaller tree ferns. The leaves of this graceful species are bipinnate, like those of the fossil; and the pinnae (thickly set with simple, alternately arranged leaflets) are opposite in the lower part of the frond, and alternate in the upper. Widely as they are separated in time, the recent South American Didymocloena and the Old Red Sandstone Cyclopterus, that passed into extinction ere the times of the Coal, might be ranged together, so far at least as appears from their forms, as kindred species. It were very desirable that we had a good monograph of the Irish Old Red plants, the contemporaries of the latter, as the completest and best preserved representatives of the Middle Palaeozoic flora yet found. Sir Roderick Murchison has figured a single pinnae of this Cyclopterus in his recently published "Siluria;" and Sir Charles Lyell, both that and one of its contemporary Lepidodendra, in the last edition of his "Elements." These interesting fragments, however, serve but to excite our curiosity for more. When urging Professor Edward Forbes on the subject, ere parting from him for, alas! what proved to be the last time, he intimated an intention of soon taking it up; but I fear his purposed monograph represents only one of many works, important to science, which his untimely death has arrested for mayhap long years to come.

In the uppermost beds of the Upper Old Red formation in Scotland, which are usually of a pale or light yellow color, the vegetable remains again become strongly carbonaceous, but their state of preservation continues bad,--too bad to admit of the determination of either species or genera; and not until we rise a very little beyond the system do we find the remains of a flora either rich or well preserved. But very remarkable is the change which at this stage at once occurs. We pass at a single stride from great poverty to great wealth. The suddenness of the change seems suited to remind one of that experienced by the voyager, when,--after traversing for many days some wide expanse of ocean, unvaried save by its banks of floating sea weed, or, where occasionally and at wide intervals, he picks up some leaf-bearing bough, or marks some fragment of drift weed go floating past,--he enters at length the sheltered lagoon of some coral island, and sees all around the deep green of a tropical vegetation descending in tangled luxuriance to the water's edge,--tall, erect ferns, and creeping lycopodiaceae, and the pandanus, with its aerial roots and its screw-like clusters of narrow leaves, and, high over all, tall palms, with their huge pinnate fronds, and their curiously aggregated groups of massive fruit. And yet the more meagre vegetation of the earlier time is not without its special interest. The land plants of the Old Red Sandstone seem to compose, all over the world, the most ancient of the terrestrial floras. It was held only a few years ago, that the Silurians of the United States had their plants allied to the Lepidodendron. But the group in which these occur has since been transferred from the Upper Silurian to the Old Red System; and we find it expressly stated by Professor H. D. Rogers, in his valuable contribution to the "Physical Atlas" (second edition, 1856), that "the Cadent [or Lower Old Red] strata are the oldest American formations in which remains of a true terrestrial vegetation have yet been discovered." It has been shown, too, by Sir Roderick Murchison, that the supposed Silurian plants of Oporto are in reality Carboniferous, and owe their apparent position to a reverse folding of the strata. I have already referred to the solitary spore-cases of the Ludlow Rocks; and beneath these rocks, says Sir Roderick (1854), "no remains of plants have been discovered which are recognizably of terrestrial origin." Scanty, too, as the terrestrial flora of the Old Red Sandstone everywhere is, we find it exhibiting very definitely the leading Palaeozoic features. Its prevailing plants are the ferns and their apparent allies. It has in our own country, as has been just shown, its ferns, its lepidodendra, its striated plants allied to the calamites, and its decided araucanite; in America, in the Cadent series, it had its "plants allied to ferns and lepidodendra;" and in the Devonian basin of Sabero in Spain, its characteristic organisms are, a lepidodendron (_L. Chemungensis_), and a very peculiar fern (_Sphenopteris laxus_).[52] But while in its main features it resembled the succeeding flora of the Carboniferous period, it seems in all its forms to have been specifically distinct. It was the independent flora of an earlier creation than that to which we owe the coal. For the meagreness of the paper in which I have attempted to describe it as it occurs in Scotland, I have but one apology to offer. My lecture contains but little; but then, such is the scantiness of the materials on which I had to work, that it could not have contained much: if, according to the dramatist, the "amount be beggarly," it is because the "boxes are empty." Partly, apparently, from the circumstance that the organisms of this flora were ill suited for preservation in the rocks, and partly because, judging from what appears, the most ancient lands of the globe were widely scattered and of narrow extent, this oldest of the floras is everywhere the most meagre.

LECTURE TWELFTH.

ON THE LESS KNOWN FOSSIL FLORAS OF SCOTLAND.