THE STEM OF CALAMITES 25 



far as anatomy goes, is simply an Equisetum with 

 secondary thickening. In order to carry the comparison 

 further, we must settle one or two points, especially 

 the course of the vascular bundles. In Equisetum 

 itself their course is exceedingly simple : a single 

 vascular bundle enters the stem from each leaf, and 



Fig. 7. — Calamitcs, sp. Radial section of a decorticated stem, with fairly thick wood, 

 showing the fistular pith, crossed by diaphragms at the nodes. X 9. From a photo- 

 graph. Phil. Trans., W. and S. Will. Coll. 1937. 



passes straight down through one internode only. At 

 the node next below, the bundle forks, and its branches 

 attach themselves to the adjacent alternating vascular 

 bundles passing out at that node. This type is often 



deposits, named provisionally C. petty curensis, groups of centripetally 

 developed wood are present on the inner side of the canals. This is a 

 point of interest, as tending to connect the Calamarieae with the Spheno- 

 phyllales, in which the primary wood is centripetal (see pp. 36 and 89). 



