180 BOTANICAL GAZETTE [MARCH 
(fig. 11). Two gaps usually occur in the same transverse section, 
and cause the xylem of the stem to appear as two curved masses 
with concave sides facing (fig. 11, G). Often only a single gap 
interrupts the cylinder (fig. 11, A), or the section may show a com- 
plete ring of xylem (fig. 12, C); very rarely, three gaps overlap. 
The leaf gaps are circular or oval and usually very large; 2 mm. 
in width by 2.5 mm. in height is an average size. The largest 
observed measures 3.23.5 mm. In general the stele is more 
compact and shows more 
definitely its cylindrical char- 
acter than in O. vulgatum. It 
is often very irregular in out- 
line; the insertion of leaf and 
root strands usually produces 
a modification of shape, as 
shown in figs. 11, 7; 12, E; 
7, J, K, etc. It is usually 
not straight, but slightly bent 
at each leaf gap in the direc- 
tion away from the leaf; this 
is undoubtedly due to the 
pressure of the young leaf. 
In diameter the stele is usually 
a little less than half that of 
the rhizome, that is, 3-5 mm. 
. eae, of E, fig. 9: x, xylem; Besides these leaf gaps, 
clon, wempeeee: eee Sbeuings Selmicly 7 
roots occur in the cylinder 
(figs. 7, J, 0; 8, J, KR; ix, B,C, J). These are more conspicuous 
in the larger rhizomes, where a gap occurs above each root; in the 
smaller specimens, gaps occur in connection with about half of the 
roots. These openings are narrower in proportion to their length 
than are the leaf gaps; they range in size from 0.20.4 mm. to 
o.5X2mm. Where a root is attached to the cylinder immediately 
below the point of insertion of a leaf, a gap is almost invariably 
produced; the leaf strands attach to the sides of this gap, which 
is therefore continuous with the leaf gap. In cases of this kind, 
2306 ry 
QRS 
feet tits 
caries 
