M. Grancl'Euiy on Calamttes and Afiferophi/Ilites. 125 



M. Brongniart was one of the first to approximate tlicin to tlie 

 Equisetacea;, guided by the analogy of their most important 

 external characters. 



Dr. Petzholdt, and subsequently M. Richter, thought that 

 decisive evidence in favour of this approximation was to be 

 found in the internal structure of these stems ; but the differ- 

 ences in their observations still left doubts on the subject, and 

 the question thus remained enveloped in much obscurity. 



The investigation that I have made of upright Calamites, 

 which are very common in the Coal-measures of the Loire, 

 will, I think, enable me to answer it in a satisfactory manner, 

 and to give a more complete definition of the Calamites. 



In the first place, the frequent presence of more or less 

 complete septa at the joints is a perfect proof that these stems 

 were fistular. 



Again, in nearly all of them we find, generally surrounding 

 the nucleus, a sort of internal epidermis, of cellular nature, 

 which is smooth or sometimes marked on the outside by lines 

 projecting opposite to the inner crests of the bark. This epi- 

 dermis, which was also found by Dr, Petzholdt in Calamites, 

 cannot have detached itself here from the inner surface of the 

 coaly {kouillijiee) envelope, of which it does not possess 

 the form, and from which it is naturally separated, when it 

 seems to have retained its relative position, by from half to 

 two millimetres. Moreover it is connected with the septa, and 

 forms with them one and the same system, whicli seems to 

 unite with the bark, where it is contracted at the level of the 

 articulations, by a sort of internal denticulations. There is 

 also, between the coaly envelope and the inner epidermis, a 

 thin stnictui'eless zone, Avhich has evidently been occupied by 

 tissue now destroyed. This tissue, which must have been lax 

 and perhaps lacunar, as it is always completely destroved, 

 certainly corresponds to the vascular tissue of the Calamites, 

 and may probably have represented in them the circle of lacunar 

 essential to the Equiseta (Duval- Jouve). 



From this it seems to me that we may define the true Cala- 

 mites as follows : — 



Stems articulated, fistular, and septate, of which the outer part, 

 which is comparatively thin, is formed by three concentric zones, 

 namely: — 1, an exterior cortical layer, now converted into coal; 



2, a thin subjacent zone of vascular tissue, now invariably destroyed; 



3, a sort of inner fining epidermis, which is carbonified. 



Cortical envelope marked interiorly with regular fiutings, inter- 

 rupted and alternate at the articulations. Inner epidermis smooth 

 or scarcely striated. Vascular cylinder thin, smooth within as 

 having been covered by the inner epidermis, and adorned on the 



Ann. db Mag. X. Hist. 8er. 4. I \>l. i v. 1 



