8 Johnstone, Catamites iCatamitina) varians, Stern/7. 



The moulds of several of the scars have been preserved, 

 and corroborate what the cast shows, leaving little doubt 

 as to the nature of the organ which fitted into the scar 

 They may be described as consisting each of two truncated, 

 rather irregular, cones, the smaller of which is seated on 

 the section of the larger, without quite covering it ; the 

 strip left outside the base is hollowed out slightly. The 

 missing apex of the small cone would be the apex of the 

 pith left in the pit, the cone itself standing for the pith of 

 the branch where it is embedded in the deeper xylem of 

 the stem. On the sloping sides of three of the small 

 cones can be distinguished arrangements of ridges and 

 furrows like those in the common pith-casts, one of which 

 this is considered to be. The ridges represent medullary 

 rays, the furrows vascular bundles. 



The larger basal cone has replaced the complete 

 branch, disorganised and removed from its loose connection 

 with the outer secondary wood. The slight trench which 

 sometimes exists at the junction of the two cones would 

 fit over the raised rim of the pit. It may simply point to 

 a line of breakage. 



Identification of Top and Bottom. 



It is necessary to determine with as much certainty 

 as possible which is the top and which the bottom of the 

 cast, as the position of the branch scars relative to that of 

 the short internode bears directly on theories regarding 

 the functional significance of that internode. 



It has been proved fairly clearly by evidence from 

 structural examples that branches emerge from the 

 external face of the secondary xylem at a slightly higher 

 level than the nodal line, leaf-traces practically at the level 



of the nodal line. It has been shown that the line s s 



{Plate) is probably the line of the leaf-scars belonging to 



