STIGMARIA 255 



however, we find an addition of radially arranged 

 secondary wood (see Fig. 1 04, 3?), and where this is the 

 case the secondary formation is always limited to the 

 side remote from the protoxylem, thus affording yet 

 another indication of monarch structure. The formation 

 of secondary wood, though rare in the free rootlets, is 



JOX. DC 



Fig. 104. — Stigmaria ficoides. Transverse section o central part of rootlet, to show 

 secondary thickening of wood, jr, primary xylem ; px, protoxylem ; -r 2 , secondary 

 xylem, limited to one side of bundle ; i.c, inner cortex. X nearly igo. From a 

 photograph by Mr. L. A. Boodle. Will. Coll. 651. 



commonly found in the rootlet-trace, where it passes 

 through the cortex of the main axis. 



The branching of the rootlets was by dichotomy. A 

 transverse section of a rootlet at the point of bifurcation 

 is shown in Fig. 105. The plane of division passes 

 through the protoxylem, and coincides with the plane of 

 symmetry of the bundle. The dichotomous branching 

 is an obvious point of agreement with the roots of 

 modern Lycopods. 



Something may now be said of other forms of 



