LECTURE TWELFTH.

ON THE LESS KNOWN FOSSIL FLORAS OF SCOTLAND.

PART II.

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 labour of future exploration. It was only last year that Mr Gourlie* of this

* Now, alas! no more. In Mr Gourlie the energy and shrewd business habits of the accomplished merchant were added to an enlightened zeal for general science, and no inconsiderable knowledge in both the geologic and botanic provinces. The marked success, in several respects, of the brilliant meeting of the British Association which held in Glasgow in September 1855 was owing in no small measure to the indefatigable exertions and well-calculated arrangements of Mr Gourlay.

city (Glasgow) added to our fossil flora a new Volkmannia from the coal-field of Carluke; and I detected very recently in a neighbouring locality (the Airdrie coalfield), 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

Fig. 125.

毛

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

Fig. 126.

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 areola; 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.

Fig. 127.

Ever since the appearance, in 1846, of Mr Binney's paper on the relations of stigmaria to sigillaria as roots and stem, 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.

Fig. 128.

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 areola. 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-aerial 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.

STIG MARIA.

I have been long desirous of acquainting myself with the true character of this latter plant (Ulodendron), but hitherto my labours 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, he 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