22 STUDIES IN FOSSIL BOTANY 



preserved at the very commencement, or even before the 

 commencement, of secondary growth, as shown in Fig. 5. 

 This is a comparatively rare stage to find, and when 

 it is found, it is nearly always in a small twig. The 

 larger stems of Catamites are rarely, if ever, met with 

 at so early a stage of development. In a twig in this 

 early condition, before secondary thickening has begun, 

 the pith is often persistent (though fistular in the 

 specimen figured), and round it we find a ring of 



Fig. 5. — Calaviites, sp. Transverse section of a very young twig, showing primary 

 structure, c, cortex ; 7'/', vascular bundles, of which there are twelve, each with 

 its canal. X nearly 40. Fhil. Trans., W. and S. Will. Coll. r56r. 



primary vascular bundles, in which the wood is but 

 little developed, and then the cortex. The whole 

 structure is strikingly like that of the stem of an 

 Equisctum} Now one of the most important questions 

 to be settled, bearing on the comparison with recent 

 Equisetaceae, is this : Are these canals in Catamites 

 really homologous with the carinal canals of an Equisc- 

 tum, or are they of a different nature, perhaps, as some 

 observers formerly thought, representing the phloem ? 

 It has been observed that, in many cases, in the 



1 Cp. Scott, Structural Botany, Part II. Fig. 39, showing the transverse 

 section of a small stem of Equiseium arvense. 



