662 



HISTORY OF THE VEGETABLE KINGDOM. 



preserved in the ironstone of Colelirookdale, the 

 following structure was apparent on sliced sec- 

 tions being made. The transverse section exhi- 

 bited a meshing, something like that of the coni- 

 fers, but with no concentric circles, and with the 

 medullary rays consisting rather of open spaces 

 Detween the other tissue, than of the common 

 niuriform tissue found in such places. The longi- 

 tudinal sections presented an assemblage of spi- 

 ral vessels of a very tortuous and unequal figure, 

 without any woody or cellular matter intermix- 

 ed. These formed a cylinder, which was sur- 

 rounded externally by a mass of organic mineral 

 matter, upon whose surface the peculiar mark- 

 ings of stigmaria were preserved, and which 

 enclosed a hollow cavity, altogether destitute of 

 mineral deposit. It would, therefore, appear, 

 that the stigmaria was a plant with a very thick 

 cellular coating or bark surrounding a hollow 

 cylinder, composed exclusively of spiral vessels, 

 and containing a rather thick pith ; and that the 

 plates of cellular tissue which preserved the com- 

 munication between the bark and the pith, were 

 of so delicate an organization, that they disap- 

 peared under the mineralizing process which 

 fixed the organic character of the woods. On 

 the whole, then, it appears that this curious and 

 unique specimen of ancient vegetation was a 

 prostrate horizontally spreading plant, with suc- 

 culent cylindrical branches, and, perhaps, leaves, 

 and that it belonged to the dicotyledonous divi- 

 sion, and, perhaps, was allied to the cactecB or 

 euphorbiacerB. The stapelias of the Cape of Good 

 Hope, and the carallumas of India, have a branch- 

 ing habit similar to that of stigmaria, but other- 

 wise their structure is different. Of rapid growth, 

 and frequenting probably a level, flat, and muddy 

 soil, with an elevated temperature, and abun- 

 dance of moisture, this plant appears admirably 

 adapted for forming those accumulations of car- 

 l)onaceous matter, of which we find the coal 

 lieds exclusively composed. From the state of 

 preservation in which the originally soft and suc- 

 culent portions of this plant are found, it appears 

 prettj' evident that it must have grown in the 

 situations, or very nearly adjoining to where it 

 now exists; or at all events, could not have been 

 far transported with any great agitation or vio- 

 lence. M. Steinhaur thus endeavours to explain 

 the probable manner in which these fossils have 

 been preserved. " Annual decay, or an accumu- 

 lation of incumbent mud, having deprived the 

 trunks of the vegetating principle, the clay would 

 be condensed by superior pressure around the 

 dead plant, so as to form a species of matrix. If 

 this took place so rapidly, that the mould had 

 obtained a considerable degree of consistency 

 before the texture of the vegetable was destroyed 

 by putrefaction, the reliquium was cylindrical; 

 if, on the contrary, the new formed stratum con- 

 tinued to subside, while the decomposition was 



going on, it became flattened, and the inferior 

 part might even be raised up towards the yield- 

 ing substance in the inside, so as to produce the 

 groove or crest on the under side, in the same 

 manner as the floor in coal works is apt to rise 

 when the measures are soft, and the roof and sides 

 have been secured. While the principal mass of 

 the plant was reduced to a soft state and gradu- 

 ally carried away or assimilated with mineral 

 infiltrated matter, the central pith being unsup- 

 ported, would sink towards the under side, and 

 this the more sensibl}^ when its texture was 

 most distinct, while its anterior extremity would 

 probably go into putrefaction with, and be lost 

 in, the more tender part of the plant. The mi- 

 neral matter introduced would now form an 

 envelope round the pith where this resisted 

 decomposition for a sufficient length of time ; 

 and when it was ultimately removed, if the sur- 

 rounding mass was still sufficiently pervious, be 

 also filled with argillaceous matter ; or if it was 

 too much indurated, be left empty, which is the 

 case occasionally. The epidermis or external 

 integument of the vegetable appears to have 

 resisted decomposition the longest, as in many 

 cases it has been preserved from putrefaction in 

 the manner necessary to change it into coal; its 

 place more frequently, however, is occupied by 

 a ferrugineous micaceous film. It therefore ap- 

 pears that the original plants must have under- 

 gone a destruction by putrefaction, and the va- 

 cuities thus occasioned been very rapidly filled 

 up with mineral matter. From this, several 

 interesting conclusions may be drawn. The for- 

 mation of these strata from the deposit of water 

 is clearly ascertained ; also, that the argillaceous 

 strata in question must have been, when origin- 

 ally deposited,of nearly the same thickness as they 

 now are, as appears from the undisturbed position 

 of the vegetables, of w-hich they were once the bed 

 and are now the tomb. On the other hand, the 

 strata of coal or slate clay, appear to have origin- 

 ated from a great number of successive depositions, 

 which must have been of a very diluted consis- 

 tence when vegetation became extinct in the 

 plants, of which they now bear the impressions. 

 All these strata must be supposed to have been 

 successively at no great depth from the surface 

 of the water resting upon them, that these plants 

 might be supplied with air ; and the situation 

 in which they are found precludes the possibi- 

 lity of any motion of that sea sufficiently vio- 

 lent to disturb the bottom. The general diflFu- 

 sion of this, and several of the following species, 

 strongly suggests the belief, that all the coal 

 strata through which they are dispersed owe 

 their existence to a similar origin." 



Favularia Tesselata. This fossil was found 

 in a bed of sandstone overlying the coal strata at 

 Garthen colliery, Denbighshire. One or two 

 other specimens have been found in other loca- 



