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.