416 VEGETATION OF THE CARBONIFEROUS PERIOD 



pression of the prostrate portions. I am not aware that they have ever 

 been found prolonged upwards from the roof of one coal-seam through 

 another one, as the coniferous * fossil discovered by Mr. Binney was. 

 This may be owing either to their generally lower stature, or more pro- 

 bably to their not being capable of surviving the geological changes 

 which that harder-wooded plant did. 



External Form of Sigillarice. — It is highly singular that this fossil 

 should be of such universal occurrence and yet be unaccompanied by 

 any evident traces of branches, leaves, flowers, or fruit, and that till very 

 recently the probability of its roots being Stigmarice was called in ques- 

 tion by most. Except, however, we assume that some Lepidodendrons, 

 which almost universally accompany Sigillarice, were the branches of 

 that genus, or that the fern fronds deposited round their bases were 

 their foliage, we cannot hazard a conjecture of the appearance of the 

 growing plant. 



In favour of certain so-called species of Lepidodendron having been 

 the young state, or the branches, of the older Sigillaria?, it may be 

 urged, that though abundant along with the latter genus, they are 

 very seldom found erect, or as it were growing, that there is no real 

 line of distinction between the two genera, and that some plants may be 

 indiscriminately referred to either. Opposed to this theory, however, is 

 the fact, that the Sigillario3 seldom or never show any tendency to ramify, 

 or present scars of fallen branches. 



Above the sudden enlargement of the base, this genus presents a 

 columnar trunk of nearly equal diameter, very different from the gra- 

 dually tapering Lepidodendron, and more like the caudex of a tree- 

 fern. The great size and peculiar form of the scars also rather resemble 

 those left by the fall of a frond than by a leaf such as the Lepidodendron 

 bore. Another fact, favouring this view of their having simulated mo- 

 dern tree-ferns in mode of growth, is the absence of any hitherto recog- 

 nized specimens of very small Sigillario? which, from being of consider- 

 ably less diameter than the old, would answer to the young f of that 

 genus, and also the absence of slender Stigmariae roots. In short, it ap- 



* This remarkable case of an erect fossil many feet long having deposited around it 

 as many feet of sandstone, followed by underclay, a bed of coal, shale, and other successive 

 deposits, is a startling proof of the rapidity with which the coal-beds were formed, of 

 the rapid decomposition of those which constituted the coal in comparison with the coni- 

 ferous wood, and of the probable composition of that deposit of very soft tissued plants. 



f This absence of young specimens may be otherwise accounted for by supposing on 

 the one hand, that the shale deposit was drifted, and that the old specimens alone with- 

 stood the effects of the transport ; and on the other, to me more probable, hypothesis, 

 that they grew on the spot, and the older specimens alone fell and were fossilized. 

 I was once inclined to consider some of the Lepidophylla as the fohage of Sigillaria, 

 but the specimens I have seen of certain fossils with those attached, and the figure given 

 by Brongniart, " Hist. Veg. Foss.,'* vol. ii. t. 23, fig. 6, are against this supposition. 



