3 8 STUDIES IN FOSSIL BOTANY 



classes of Pteridophyta will be emphasised in later 

 chapters. 



5- The Leaves. — The leaves of the Calamarieae 

 were in all cases arranged in whorls, and were usually of 

 a simple acicular or lanceolate form, though in the genus 

 Archaeocalamites they were forked (Figs. 30, 31). It is 

 often stated that the leaves of the Palaeozoic Equisetales 

 differed from those of their later successors in being 



Fig. 12. — Catamites, sp. Transverse fracture through a node, showing leaf-sheath and 

 free tips of leaves, each with its vein. Commissural bundles also shown, x about 2. 

 From a specimen in the possession of Mr. Parker of Rochdale. (G. T. G.) 



free, and not united to form a sheath. It is no doubt 

 true that the free laminae were much more developed 

 in the Calamarieae than in recent Horsetails, but in 

 several cases there is good evidence for the presence of 

 a coherent sheath at the base. This is clearly shown 

 in Fig. 12, which represents the node of a Calamite, 

 exposed in transverse fracture on the surface of the 

 matrix. The greater part of the whorl of leaves is 

 shown, and they are evidently united into a continuous 



