1-2 



DESCRIPTIVE CATALOGUE 



The leaves are not only confined to one side of each stem, but 

 occur in two regular alternating rows in rapid succession, so 

 that sometimes two leaf-traces occur in the same transverse 

 section. Nevertheless, though the position of the leaves on 

 each small stem is so restricted, the orientations of the leaves 

 on the various stems composing one " plant," bear no relation 

 to each other and appear to arise at haphazard in any direction 

 (text-fig. 2). 



DETAILED ANATOMY. The vascular system of each of the unit- 

 stems is a single solenostele which is slightly oval in outline. 

 The ring of the solenostele is frequently broken by the leaf- 

 traces, but the leaf-gaps thus formed are small, as they are 

 rapidly closed up. The xylem ring, except just at the point of 

 preparation for the departure of the leaf-traces, consists of 8 lo 

 tracheids in thickness, with which are mixed some smaller 

 elements of soft-celled parenchyma. Protoxylem element! 

 have not been identified, and the majority of the trache;e appear 

 to be scaluriform. 



The phloem is not properly preserved in recorded specimens, 

 but Kidston & (jwynne-Vaiighan see " no reason to doubt its 

 existence on either side of the solenostele." 



An unmistakable endodermis is present, the individual small 

 cells of which it is composed being well preserved in good 

 specimens; but frequently it is represented only by a dark line 

 of carbonaceous matter. Such a dark line often marks the 

 outline of the steles even in very poorly preserved specimens. 



The cortex consists of two zones: an inner, comparatively 

 parenchymatous, and an outer, sclerenchymatous, series of cells. 

 The stems branch not infrequently, and when that takes place 

 the solenostele is medianly constricted and dichotomises quite 

 simply. 



The stems, therefore, are individually very simply organised, 

 and their peculiarity is shown in their leaf-arrangement and in 

 their aggregation into a false stem. 



The leaf-trace is a simple horse-shoe, and is of large si/e in 

 proportion to the main axis (see text-fig. 3). These leaf-traces 

 only arise on one side of the stem, and there they occur in two 

 rows alternately on either side of the median plane, and arising 

 very close to each other. 



The side opposite to the leaf-trace-exits in any stem, gives 



