194 BOTANICAL GAZETTE [MARCH 
trace (which usually comes off divided), a root stele, the com- 
missural strand, and the medullary strand. A section of the 
sporophyte at this stage is shown in fig. 6. 
In the more advanced specimens studied the exact stage could 
no longer be determined, owing to the distortion and decay of the 
lower regions. The difference between these and the previous 
stages was shown in the earlier bifurcation of the leaf traces, which 
may take place as the leaf is preparing to leave the central strand. 
Fic. 8 
Fics. 7, 8.—Fig. 7, diagram showing root attachment to commissural strand 
before latter has joined central strand (only xylem shown); c, central strand; ms, 
lary strand; cs, commissural strand; r, root stele; /, dividing leaf trace; X38; 
fig. 8, diagram showing two roots on same level; one joined on central strand 
and other on commissural strand: c, central strand; ms, medullary strand; cs, com- 
missural strand; 7, root stele; /, bifurcated leaf trace; X38. 
The commissural strand also appears earlier, in some cases before 
the leaf trace is free. The two branches of the leaf trace bifurcate 
while within the cortex, so that here four strands from one leaf trace 
enter the stipular region. Considerable variation was observed in 
the attachment of the commissural strand. This may run up farther 
before merging with the central strand, and the root which is usually 
attached to the central strand may be inserted on the commissural 
strand (fig. 7). In some cases also a root may appear higher on 
the central strand, bringing two roots almost on the same level 
(fig. 8). In such cases apparently the two roots are related to one 
leaf trace. In following out the series, however, it was found that 
