Feb. 1,1925 
Vegetative Organs of Sugar Cane 
209 
bundles, except in the meristematic 
region of the stem apex. Longitudinal 
sections through such a region show 
numerous bundles passing from the 
stem into the leaves. The largest of 
these bundles pass gradually from the 
periphery of the stem to the center, and 
from here, in a curve with the convex¬ 
ity upward, out into the leaf (pi. 12, 
A and B). The smaller bundles pene¬ 
trate less deeply, and the smallest re¬ 
main near the periphery. In regard to 
the length of the individual leaf traces 
the same sequence is observed, that is, 
the largest bundles are also the longest 
and pass independently through about 
eight internodes; whereas the smaller 
bundles are correspondingly shorter, 
and the smallest cortical bundles termi¬ 
nate in the same internode. Strasbur- 
ger (16, p. 328) found in Zea that the 
longest leaf traces pass through six inter¬ 
nodes. In the sugar cane, the writer 
has followed a number of the large 
traces through seven and even eight 
internodes; their absolute length, how¬ 
ever, he was unable to determine with 
certainty. 
The course of the leaf traces is still 
further complicated in that they de¬ 
scribe a spiral in their passage through 
the stem. For this reason it is very 
difficult to follow the entire length of a 
trace in longitudinal sections. This 
peculiar course of the traces is also re¬ 
sponsible for the crossing of traces, 
which is so noticeable in radial sections 
(pi. 12, B). The traces of the higher 
leaves will cross those going to lower 
leaves and the crossing will be the more 
striking the thicker the stem and the 
closer the leaves. In the mature stem, 
as has been noted, the bundles run ap¬ 
proximately parallel to each other, but 
this is accounted for by the fact that 
the length of the internodes has in¬ 
creased extremely, and since the large 
traces pass through many internodes 
the seemingly parallel course of the 
leaf traces closely approximates the real 
situation. 
Further complications of the course 
of the vascular bundles are seen in the 
node in connection with the vascular 
supply of the roots and the axillary 
bud. But, whereas the root connec¬ 
tions are derived mainly from the peri¬ 
pheral zone of bundles, the numerous 
traces going to the bud anastomose 
with the bundle system of the entire 
cross section of the stem. 
This net of horizontal traces (pi. 11, 
A) may serve in part other purposes 
besides the connection of the buds and 
roots with the vascular arteries of the 
stem and the leaves. Since there is 
located above the Keimring the inter¬ 
calary meristem, where active growth 
takes place, these numerous horizontal 
bundles may serve to conduct food 
material to this meristematic zone, as 
suggested by Haberland (7, p. 338). 
THE LEAF SHEATH 
A cross section through the middle 
of the sheath, about midway between 
sheath and blade joint, shows radial 
rows of vascular bundles, embedded in 
fundamental parenchyma (pi. 13, D). 
The cells of the latter, however, are 
mostly broken down, so that the vas¬ 
cular bundles are actually separated 
radially by large air cavities. The vas¬ 
cular bundles lie closer to the outer 
epidermis (morphologically lower sur¬ 
face) than to the inner one (pi. 14, D). 
There are bundles of two or sometimes 
more different orders of size alternating 
with one another. The large ones 
occupy approximately the center of the 
sheath in a cross section, while the 
smaller ones are close to the outer epi¬ 
dermis and may even touch it. The 
large bundles frequently consist of two 
or even three superimposed groups (fig. 
4) connected by bands or caps of scler- 
encl^ma. They have the typical 
shape described for the bundles of the 
stem, except that in the sheath the 
phloem is more strongly developed 
(pi. 4, B). The entire bundle is sur¬ 
rounded by a sclerenchyma jacket 
which is a continuation of the sheath 
of the stem bundles. The smallest 
bundles, which always lie closest to 
the outer epidermis, consist largely 
of a mass of sclerenchyma inclosing a 
few vascular elements. 
The parenchyma cells which form 
the radial prolongation of the bundles 
in the direction of the inner epidermis 
(pi. 15, E), show a more or less definite 
arrangement and terminate in a small 
mass of sclerenchyma (pi. 14, D), which 
is separated from the inner epidermis 
by a row of narrow, parenchymatous 
cells. 
The base of the sheath, also called 
the sheath-joint (pi. 1 B and pi. 13, A), 
is swollen and lacks the projecting 
veins of the sheath proper. Structur¬ 
ally it reflects the molding influence of 
its location which demands great elas¬ 
ticity of the tissues coupled with late 
maturation. Increase of flexibility is 
attained by transformation of the scle- 
renchymatous elements of the bundle 
into collenchyma, while greater 
strength is at the same time afforded by 
the disappearance of the large air cavi¬ 
ties, and the development of small- 
