RACHIOPTERIS CTLINDRICA. 63 



the convex side of the xylem. It is somewhat tantalising that the pre- 

 parations should fail at this important point, because, as will be seen 

 below, the nature of the member to which this stele belongs depends, 

 at least in part, upon the symmetry of the stele. It is important, 

 therefore, to decide whether the latter is radially or bilaterally 

 symmetrical. 



Lastly, in No. 115, we have two distinct and complete structures, 

 lying near to one another, whose steles correspond respectively to those 

 found in the same axis in No. 101. 



In No. 105 (Fig. 2), in addition to the two steles already described, 

 a third structure is found in the cortex, which is obviously some organ 

 which, originating at or near the bifurcation, is on its way from the 

 central cylinder to the surface Coming off obliquely, its section is an 

 oblique one, but in it we can easily distinguish both a central cylinder 

 and a cortex. The cortical cells seem to have had thin walls and 

 copious cytoplasmic contents, as if full development had not yet been 

 attained. The central cylinder is not at all well defined, but I suspect 

 it carried a diarch xylem strand. The real nature of this organ is not 

 quite certain, but its endogenous origin leads me to thing it is a root, 

 Moreover, in several preparations, Nos. 102 and 103, for example, 

 sections of the principal axis are accompanied by sections of structures 

 that are almost certainly roots, and have some resemblance to the organ 

 in question. 



Division of the Axis. 



Looking at the whole series of sections with dividing steles, it seems 

 scarcely open to doubt that while in equal division we hasre an indica- 

 tion of dichotomous branching of the axis, in which the two members 

 are strictly homologous with each other and their common podium, in 

 unequal division of the stele we have an indication of the formation of 

 some lateral organ which is not homologous with the axis from which 

 it arises. 



As to the morphological nature of this lateral organ or appendage, 

 the evidence to hand is not sufficient to justify any definite conclusion. 

 The suggestion that it is a foliar organ naturally and readily occurs, 

 and that may be its character. It would be in favour of this view if 

 the suspicion expressed above that the stele is not radially symmetrical 

 could be converted into certainty, and this view is supported by the 



