58 



PAL.5]0NT0L0GICAL B0TA:NT. 



or scarcely striated. Vascular cylinder thin; outer surface 

 of bark more fully fluted and articulated than the inner surface. 

 Carruthers gives the following description of the structure 

 of a species of Calamite which he examined : — The stem was 

 composed of a central medulla, which disappeared with the 

 growth of the plant, surrounded by a woody cylinder, com- 

 posed entirely of scalariform vessels, and a thin cortical layer. 

 The medulla penetrated the woody cylinder by a series of 

 regular wedges, which were continued, as delicate laminas of 



Fig. 46. 



one or two cells in thickness, to the cortical layer. The cells 

 of those lamince were not muriform ; their longest diameter 

 was in the direction of the axis. The wedges were continuous, 

 and parallel between each node. As the axial appendages 

 were produced in whorls, the only interference with the regu- 

 larity of the tissues was by the passing out through the stem 

 at the nodes of the vascular bundles which supplied these ap- 

 pendages. As the leaves of each whorl were (with one or 



Fig. 46. Vertical stems of fossil trees, Calamites chiefly, found in 

 the coal-measures of Treuil, near Saint Etienne. 



