84 REPORT — 1855. 



We stand on the further edge of the great Floras of bygone creations, and have 

 gathered but a few handsfull of faded leaves, a few broken branches, and a few de- 

 cayed cones. 



The Silurian deposits of our country have not yet furnished us with any unequivo- 

 cal traces of a terrestrial vegetation. Professor Nicol of Aberdeen, on subjecting to 

 the microscope the ashes of a Silurian anthracite which occurs in Peebles-shire, 

 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 marine vegetation 

 notwithstanding. 



Associated with the earliest ichthyan remains of the Old Red Sandstone, we find 

 vegetable organisms in such abundance, that they communicate often a fissile cha- 

 racter to the stone in which they occur. But existing as mere carbonaceous mark- 

 ings, their state of preservation is usually so bad, that they tell us little else than 

 that the antiquelj'-formed fishes of this remote period had swum over sea-bottoms 

 darkened by forests of algae. 



The immensely developed flagstones of Caithness seem to owe their dark colour 

 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 terrestrial vegetation in this deposit are greatly scantier than those 

 of its marine Flora ; but they must be regarded as possessing a peculiar interest, as 

 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 the author has elsewhere described as having much the appearance 

 of one of our smaller ferns, such as the maidenhair spleenwort or dwarf moonwort. 

 But the 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 a little work on 'The Old Red Sandstone' in 1841, as exhibit- 

 ing 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 spe- 

 cimen 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 presented 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 ?" 



The Caithness flagstones have furnished one vegetable organism apparently higher 

 in the scale than those just described, in a well-marked specimen of Lepidodendron, 

 which exhibits, like the Araocarian of the Lower Old Red, though less distinctl}', 

 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 latter place from the north. Above this gray flagstone 

 formation lies the Upper Old Red Sandstone, with its peculiar group of ichthyic 

 organisms, none of which seem specifically identical with those of either the Caith- 

 ness 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 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 the fishes of the Lower, or Caithness and Cromarty 

 platform, than they do those of the Forfarshire and Kincardine one. In the upper- 



