AS COMPARED WITH THAT OF THE PRESENT DAY. 417 



pears far from impossible, that the Sigillarice was strictly Acrogenous 

 (increasing not laterally but in length) in its growth, that it at first 

 assumed nearly its full diameter, as a tree-fern or palm does, throw- 

 ing out at the same time its stout Stigmarice roots, which we know 

 to be of a very uniform diameter in all stages, and throughout their 

 whole length (points which will be dwelt upon in a separate essay). 

 It may further be conjectured, that the Sigillaria, as it grew upwards 

 with some rapidity, threw off the lowest fronds successively, leaving 

 the broad scars on the stems. 



I do not attempt to enter into any further or more rigid comparison 

 between tree-ferns and Sigillaria, confining the above only to what may 

 subsist between the mode of growth of these two very distinct tribes of 

 plants, which does not necessarily indicate a close botanical affinity 

 between them. 



The succulent nature of the Sigillarice, which I have elsewhere dwelt 

 upon, can hardly be considered an objection to these trunks having 

 been the supports to the fern fronds* so abundantly scattered about their 

 roots ; for it may be remarked, that the stipites (stems of the fronds 

 themselves) appear to have been of a succulent texture likewise, if we 

 may judge of their invariable compression in the shales, and the rarity 

 of their occurrence in the nodules of iron-stone, &c, in a state that 

 shows structure. Succulent caudices (subarborescent) and stipites, too, 

 are further characteristic of some of our largest and most coriaceous - 

 fronded recent ferns, as the Marattiacece and Daneacece. In these tribes, 

 the succulence of their organs is remarkably contrasted with the woodi- 

 ness of those of most other ferns, the fronds of which are already assumed 

 (on characters drawn from the fructification only) to occur in the coal 

 formation. 



A yet more remarkable and anomalous structure in Sigillarice than 

 either that of their stigmaroid roots or fluted stems was pointed out to 

 me by Mr. Binney, of Manchester, to whom I am mainly indebted for 

 all I know of the most important features of this genus, and whose in- 

 vestigations of their habit, mode of growth, and of their connexion with 

 the Stigmaria are beyond praise. f This is the curious crucial mark 



* This is, I believe, the opinion of Mr. Binney, who mentioned it to me with some 

 hesitation arising from his never having found the fronds attached, and from his having 

 had no opportunity of comparing the Sigillarice with existing tree-ferns. 



f In the Manchester Museum there is a room almost entirely devoted to illustrating 

 the botany of the coal formation. The original specimens of some Sigillaria and models 

 of others of the natural size, collected and transported with great labour, and arranged 

 under Mr. Binney's direction, present to the eye the grandest features of the coal flora. 

 Accustomed as I had been to see these fossils in situ, both in the pits and in quarries, I 

 had previously no adequate conception of their gigantic size, nor of the rapidity with 

 which coal may have been formed, if the tissues of these vegetables were as lax as I sup- 

 pose them to have been. 



