THE FLORA OF THE COAL FORMATION. 441 



believe that the statements often found in geological books to the 

 eflfect that the Catamites were smooth externally, and that tlic sup- 

 posed jointed stems are only casts of the pith, are true o( Calamodendron 

 only, and proceed from confounding that genus with Calamites. 



A Calamodendron as usually seen is a striated cast with frequent 

 cross lines or joints; but when the whole stem is preserved, it is seen 

 that this cast represents merely an internal pith-cylinder, surrounded 

 by a woody cylinder composed in part of scalariform or reticulated 

 vessels, and in part of wood-cells with one row of large pores on each 

 side. External to the wood was a cellular bark, and the outer surface 

 seems to have been simply ribbed in the manner of Slc/illaria. It so 

 happens that the internal cast of the pith of Calamodendron^ which is 

 really of the nature of a Stemhergia, so closely resembles the external 

 appearance of the true Calamites as to be constantly mistaken for them. 

 Most of these pith-cylinders of Calamodendron have been grouped in 

 the species Calamites approximatus ; but that species, as understood 

 by some authors, appears also to include true Calamites* which, how- 

 ever, when well preserved, can always be distinguished by the scars 

 of the leaves or branchlets which were attached to the nodes. 



Calamodendron would seem, from its structure, to have been closely 

 allied to Sigillaria, though, according to Unger, the tissues were 

 differently arranged, and the vvoody cylinder must have been much 

 thicker in proportion. 



The tissues of Calamodendron are by no means infrequent in the 

 coal, and casts of the pith are common in the sandstones; but its 

 foliage and fruit ai'C unknown. They probably resembled those of 

 Sigillaria. 



Class of CRvrTOGAMS. 



1. EqiiisetacecB. 



1. Calamites. — These curious plants are by no means to be confounded 

 with those last noticed. Their stems Avere slender, ribbed and jointed 

 externally, and from the joints there proceeded, in some of the species, 

 long, narrow, simple branchlets ; and, in others, branches bearing 

 whorls of small branchlets or rudimentary leaves. The stem was 

 hollow, with thin transverse floors or diaphragms at the joints, and 

 it had no true wood and bark, but only a thin external shell of fibres 

 and scalariform vessels. The Calamites grew in dense brakes on the 

 sandy and muddy flats, subject to inundation, or perhaps even in the 

 water, and they had the power of budding out from the base of the 

 stem, so as to form clumps of plants, and also of securing their foot- 



* See Geiiiitz, '• Steinkolileii fdriniitiim iu Saclisen." 



2 F 



