178 BOTANICAL GAZETTE [MARCH 
fuse at one margin, forming a half-cylinder of xylem (fig. 8, £). 
Two roots are usually given off somewhat farther up (fig. 8, J), 
and the margins of the gap come together at about the level of the 
base of the first leaf. 
In a single instance, three strands arise from the three poles of 
atriarch root. These fuse just below the point of connection of the 
first root to form a large strand of semicircular cross-section. The 
gap between the margins closes just below the level of the first leaf. 
In another specimen, two strands separate from each of two of the 
1G. 8.—Development of stem stele from two strands; only the xylem is shown: 
px, protoxylem strands of parent root; rt, root traces; X12. 
protoxylem strands of a tetrarch root. These four organize a stele 
in the manner described above; the opening in the side is closed 
rather late, at the level of the top of the first leaf gap. 
The stem stele is organized in a distinctly different way in four 
cases. A series of sections through one of the specimens from 
below upward is shown by fig. 9. In this case, the xylem mass of 
one pole of a diarch root begins to enlarge (fig. 9, A-C). After 4 
time, medullation of the enlarged xylem strand occurs by the 
appearance of parenchyma near the center (fig. 9, D, £, fig 10). 
The endodermis disappears on the side away from the unchanged 
