220 
Journal of Agricultural Research 
Vol. XXX, No. 3 
In their further development these 
cells either merely enlarge as, for 
example, the cells of the inner epi¬ 
dermis of the leaf sheath and the 
ligule, or they undergo further modifi¬ 
cations. In the latter case each cell 
divides unequally giving rise to a long 
cell and a short cell. The long cell 
elongates still further, while its walls 
become thick and strongly undulated. 
The short cell either ceases growth and 
undergoes silicification, or, according 
to Pfitzer (14) , it becomes the primor- 
dium of a hair or stomate. 
In the development of a hair the 
peripheral tangential walls of the 
epidermal cell begin to show marked 
apical growth. As the cell enlarges, 
the nucleus divides (pi. 14, A). The 
binucleate condition exists until the 
cell has attained approximately its full 
length; a wall then develops which 
divides the hair into two more or less 
equal parts. In the later develop¬ 
ment, the base of the hair becomes 
lignified, while in the apical region 
there is often found a slight brownish 
precipitate. The first-formed hairs are 
commonly two-celled. They are al¬ 
ways delicate and ephemeral. Short 
unicellular hairs with thick, lignified 
walls are characteristic of the more 
mature organs. In the region of the 
sheath and blade-joints the unicellular 
hairs attain a considerable length, 
which reaches its maximum in the 
fringes at the base of the ligule. 
The short cells of the epidermis next 
to the veins of the leaf and more 
sparingly in other regions continue 
development into stomates. The short 
cell constitutes the stomate mother cell 
which by further division gives rise to 
the two guard cells. The two sub¬ 
sidiary cells of the stomate are formed 
as lateral outgrowths from the adjacent 
parenchyma cells. With the forma¬ 
tion of the stomatal chamber and the 
separation of the wall between the two 
guard cells the development of the 
stomate is complete. The stomates of 
the inner epidermis of the leaf sheath 
differ from those of the stem and leaf 
blade in that the subsidiary cells are 
very broad; the guard cells too appear 
to be slightly different and the stomatal 
pore instead of being a narrow cleft of 
even width is more or less oval (pi. 19). 
The epidermal cells of the stem 
remain thin-walled for a long time, 
even after the vascular bundles are fully 
developed. Eventually, however, the 
walls thicken, especially the outer 
ones, which in addition become cutic- 
ularized and finally covered with a 
layer of wax. The epidermis of the 
leaf blade and the outer epidermis of 
the sheath also become thick-walled 
and lignified. 
SUMMARY 
The vascular bundles of the sugar 
cane are of the normal monocot type, 
rhomboid to oval in cross section and 
surrounded by a well-marked scleren- 
chymatous sheath which is enlarged on 
the phloem and xylem poles into bundle 
caps. Phloem and xylem are disposed 
collaterally in relation to each other. 
Deviations from this arrangement are 
observed in the node and the lower 
leaf sheath, since here certain of the 
bundles show a more or less amphivasal 
structure. True amphivasal arrange¬ 
ment, however, is found only in the 
larger traces of the buds. In the lower 
leaf sheath a pseudo-amphivasai ar¬ 
rangement is sometimes produced by 
the formation of compound bundles. 
The xylem is composed of some pro- 
toxylem and two large pitted vessels. 
The protoxylem forms a short radial 
row of annular and spiral elements. 
It is more extensive in the node than 
in the internode and reaches its maxi¬ 
mum development in that part of the 
leaf traces which runs horizontally in 
the node. The large pitted vessels of 
the metaxylem also tend to increase in 
number as the vascular bundle passes 
through the node; the large horizontal 
leaf traces on the other hand lack the 
large vessels altogether. The inter- 
nodal bundles, except those near the 
periphery, and the large bundles of 
the leaf sheath and the blade possess a 
more or less conspicuous protoxylem 
lacuna. The lacuna is absent in the 
bundles of the node, the peripheral 
bundles of the internode, and the 
smaller bundles of the leaf. 
The phloem consists of sieve tubes 
and companion cells. It is most ex¬ 
tensive in the bundles of the node and 
the leaf sheath, but least conspicuous 
in the smaller bundles of the leaf blade 
and the peripheral bundles of the in¬ 
ternode. Changes in the phloem con¬ 
sist in obliteration of the proto¬ 
phloem, which is most pronounced in 
the large bundles of the leaf, probably 
because of the development of an inner 
fibrous sheath above the phloem cells 
and in a lignification of certain portions 
of the mature phloem tissue. Lignified 
metaphloem is most frequently ob¬ 
served in the large bundles of the node 
and in the Keimring. 
The vascular bundles are surrounded 
by a scierenchymatous sheath which is 
most strongy developed on the inside 
