22 
the center of the leaf is always a little larger than the lateral ones, 
The bundle of the scutellum now appears distinctly in all sections 
taken through the region of the plumule. N represents a section taken 
directly underneath the plumule-sheath. The bundles of the sheath 
have united with those of the leaves and appear very irregular, with a 
secondary radicle appearing on each side. A little lower down a third 
secondary radicle is seen on the side of the axis next to the scutellum, 
The axis now for a considerable distance presents the appearance shown 
in P and Q, with two distinct, separate, vascular bundles in the center. 
At the base of the long axis one of these bundles situated nearest to 
the scutellum joins with the bundle of the latter, as in S, while the 
other continues down into the main radicle, as in T. This seems to 
prove conclusively that the plumule-sheath is not an independent leaf, 
but that it belongs to the scutellum. 
There is no difference between this group and the first, represented 
by the Agrostidew, except that between the insertion of the plumule- 
Sheath and the scutellum there occurs a very long axis representing 
the first node. 
3. The plumule-sheath is inserted on the axis at the base of the plu- 
mule, but its fibro-vascular bundles are not directly connected with 
that of the scutellum: Zea, Coix, Pennisetum, Paspalum, Panicum, and 
Spartina. Zea mays may be taken as typical of this arrangement of 
the vascular system, as shown by a series of sections from the radicle 
to the plumule (figs. 3, and 4 A-F, Pl. I). Fig. 4 A represents a cross 
section through the main, radicle. There are two systems of vessels, 
consisting of six large ones toward the center and about sixteen smaller 
ones on the outside, which, along with their conjunctive tissue, make. 
up the central cylinder. Section B, taken somewhat higher up, above 
the region of coleorhiza shows the axis with its bundles beginning to 
form round the periphery of the central cylinder, the two systems of 
vessels remaining the same as in the radicle. The dark portions of the 
scutellum are sections through the lateral branches of the scutellum 
bundle. These peripheral bundles widen and come closer and closer 
to the center until they reach the condition figured in C, where there 
18 an irregular mass of vascular strands and bundles with only a few 
of the vessels. Immediately above this the bundles arrange them- 
selves round the periphery, leaving only a few in the center, while a 
vascular strand branches off and penetrates through the cortical 
parenchyma into the scutellum, where it divides into an ascending and 
descending branch, as in D. The large vessels have returned to their 
original position, while the smaller ones have become fewer, and are 
arranged irregularly nearer the center. At E, a section taken through 
the upper part of the scutellum, two radicles emerge from the axis to 
se his boo i bundles are found both in the periphery and 5 
© center of the cylinder. The @xis now continues in a regular form 
with its two systems of vessels and bundles arranged in the periphery, | 
