OF CAL AMITE AN STROB1LU3. 255 



that the latter structure originally filled the contiguous de- 

 pression in the peripheral portion of the bractigerous disk. 

 It may be observed that, in all the vertical sections, the disk 

 is seen to receive vascular and. cellular contributions, both 

 from above and below the node to which it belongs, though 

 chiefly the latter — a condition not unlike what occurs in 

 the reproductive spikes of many living Equisetaceae, where 

 a similar thickening of the sporangiophores takes place. 



Fig. 7 exhibits the right half of a vertical section like 

 the last ; but, from its importance, it is represented as 

 more highly magnified, a is part of the medullary cavity, 

 in immediate contact with which is the prosenchymatous 

 tissue, everywhere forming the innermost part of the 

 solid woody axis. The cells are oblong, and of various 

 lengths. Sometimes they have rectangular septa, but 

 more frequently they present obliquely overlapping ex- 

 tremities. The structure of the outer part of the woody 

 cylinder varies accordiag to the line in which the vertical 

 section has been made. We here find that the axis begins 

 to enlarge at the centre of the internode, e', and continues 

 to do so gradually as we ascend to the node above. The 

 enlargement is the result of additional prosenchymatous 

 cells (c) added to the exterior of the longitudinal ridges. 

 At / the section has laid open a narrow segment of one of 

 the larger pyriform canals, fig. 3/, throughout a great part 

 of its length ; whilst at c" we have the thin film of prosen- 

 chyma which has separated that canal from one of the 

 smaller ones, fig. 3 g. At the lower part of the section we 

 have some important features exhibited. At e is the node, 

 marked by a constriction of the medulla, arched over by 

 a group of reticulated vessels. These are identical, both 

 in their structure and arrangement at this point, with 

 what I have described in Calaynopitus. They spring from 

 the medulla below the node, at an oblique angle, and 

 arch over the node, returning to the medullary tissue at 

 nearly the same angle as that with which they arose; but 



