Scutellum in Zea Mai's. 
119 
the scutellum is wanting in the fourth series of sections — that cut through 
the embryo of a dry seed — but glands are found near the beginning of 
this series, and they probably stand above the corresponding line. In 
all four series glands are more numerous in the middle zone than below 
it, but they are occasionally found even at the extreme base. They are 
also more frequent on the wings of the scutellum than on or very near 
the median spine (Figs. 6-8). 
We have not followed the development of these glands, for they are 
fully formed in the ripe seed, which is the youngest stage we have 
examined. Their appearance in section suggests that they are infoldings 
of the epithelium. 
Vascular System of the Scutellum. 
The bundles of the scutellum are inserted on the stele of the axis at the 
great vascular junction on which the root-insertion r r is marked in Fig. 1, 
PI. V. The bundle shown in that figure as entering the lower part of the 
scutellum is one of several large vascular branches which ramify there and 
supply its needs. There is no main bundle in this part of the scutellum, 
and the xylem of the various branches never becomes completely lignified. 
A single massive bundle runs from the vascular junction into the upper 
part of the scutellum, and ends just below the extreme apex. This bundle, 
with its slender but numerous branches, constitutes the entire vascular 
system of the upper scutellum. A few days after germination its xylem is 
completely lignified, standing out sharply in stained sections. 
Just above its insertion on the axis the main bundle is circular or oval 
in transverse section, and is surrounded by an unthickened endodermis. It 
lies near the ventral surface of the scutellum, towards which its small 
xylem group is directed. The phloem group is very large (Fig. 1 5). In 
the seedling figured there is hardly any indication of a division into two 
masses, but in others the two groups of phloem are quite clearly marked, 
and are partially divided from each other by a group of parenchymatous 
elements with wide lumen and slightly thickened walls which occupies the 
position of the sclerenchyma in the bundle of the mature stem. Such 
elements are present in the section drawn in Fig. 15 (scl.), but are not 
gathered up into a compact group. 
The phloem proper or ‘ soft bast ’ does not show the regular geo- 
metrical pattern characteristic of the transverse section through a mature 
bundle. 
Sections which cut the axis of the seedling transversely pass longi- 
tudinally through the main scutellum bundle as it enters the axis. Spiral 
and annular tracheids are the first xylem elements to be lignified. In 
a six days’ seedling (A 9i Fig. 9) many larger tracheids are also present, 
