357 
leaf. Here the leaf trace forks at the top of the leaf suggesting 
the same condition as in B. lunaria (Bruchmann 7). 
Lobes are formed at this leaf at a little older stage, as the third 
leaf is further advanced. The form of these lobes may be clo- 
sely traced in a series of transverse sections (Fig. 28). We see 
that the sheath of the cotyledon surrounds the leaf entirely. 
This is not the case in B. virginianum or B. obliquum. 
The form of apical cell of the stem seems to be variable. 
Fig. 26 shows a transverse section through the stem tip. The 
apical cell (shaded) is a three sided pyramid. The leaf trace 
of the second leaf is already advanced, and the initial stages of 
of the third leaf can be seen at the right side of the slit. 
Fig. 37. 
The oldest plant of the material was cut into a complete series 
of transverse sections (Fig. 39, left to right; Fig. 40, right to 
left). Starting at the upper side of the plant, the formation to 
the stele is as follows: 
The leaf traces of first leaf and second leaf, in their advanced 
stages consisting of two separate xylems, appear at a lower 
plane as two simple strands; the trace of the cotyledon keeps 
its double character a little longer. At this plane a root trace 
enters and coalesces with the trace of the second leaf. At this 
level the endodermis becomes conspicuous. Xylem of root and 
leaf form together a horseshoe-shaped xylem. Another root 
trace joins the stele. This trace belongs to the first leaf. The 
three traces form a closed xylem ring, surrounded by an endo- 
dermis. Further down four other roots enter, disturbing the 
complete xylem ring and forming root gaps. The stele consists 
