so STUDIES IN FOSSIL BOTANY 



namely the genus Calamites. Included in this group 

 there are many so-called species, though they are 

 very difficult of distinction. As to the sense in 

 which the name Calamites is used here, the char- 

 acteristics of the genus will become evident as we go 

 on, and I will only mention now that Calamites, as the 

 name is employed in the present book, is equivalent 

 to the Arthropitys of many palseobotanists, especially in 

 France. 



If we examine, by means of sections, the ordinary 

 form of stem of a typical Calamite in the petrified 

 condition, with well-preserved structure, we find the 

 following characters : the pith is generally hollow, 

 only its outer zone being preserved, and the definite 

 internal limit which we often find to this persistent 

 zone, leads us to believe that the pith was fistular 

 during life, and that the cavity is not merely the result 

 of decay. In Fig. 4 part of a transverse section 

 of a Calamitean stem is shown. The pith, as usual, 

 was hollow, but only the persistent layers of the 

 external part are represented. Around the pith is a 

 ring of collateral vascular bundles ; here, as in the 

 great majority of specimens, a considerable mass of 

 secondary tissue has already been formed, so that each of 

 the bundles has assumed a more or less regular wedge- 

 like form. On the inner limit of each, we find, with the 

 rarest exceptions, a definite canal, so that the whole 

 appearance recalls very much that of a section of the 

 stem of one of the living Equiseta. The question 

 whether this appearance indicates a real identity of 

 structure is one which we shall have to consider 

 presently. In most specimens everything outside the 



