1901} ERIOCAULON DECANGULARE 35 
structure as in the proper leaf. The tubular portion, however 
possesses an epidermis of several (three) layers on its morpho- 
logically ventral face, and this epidermal tissue is homogeneous 
in structure, the cells being of the same size and shape throughout. 
The dorsal epidermis consists of only one stratum, and the cells, 
are about the same size as those of the ventral epidermis. The 
mesophyll is very open on account of wide lacunes, as in the 
proper leaf. The mechanical tissue is developed further in the 
prophyllum than in the other leaves in having larger groups on 
the dorsal face and in being distinctly thick walled, almost like 
collenchyma. The mestome bundles are surrounded by this tis- 
sue, and also by the inner sheath, which is much less differen- 
tiated, however, in this leaf, being totally absent in the smallest 
bundles. Furthermore, a somewhat weaker development of the 
hadrome and leptome is to be seen in this portion of the pro- 
phyllum. It may be stated that the structure of the collen- 
chyma was plainly followed to several of the cells of the outer 
sheath ; thus there seems little doubt that this sheath actually 
represents a part of the mechanical tissue itself, instead of being 
a specially developed parenchyma sheath. 
The little blade resembles very much that of the proper leaf, 
in regard to the epidermis with its hairs and stomata, and the 
mesophyll with its lacunes; while the collenchyma is separated 
from the dorsal epidermis by strata of small palisade cells. 
There is the same distinct thickening of the collenchyma, and 
very plainly so where it surrounds the nerves; the inner sheath 
is but very incompletely developed in this portion of the leaf. 
The mestome bundles are almost orbicular in transverse section, 
and exhibit the same difference in relative size as described 
above; and finally anastomoses more frequently occur in the 
Prophyllum from apex to base. Thus the inner sheath is present 
also in the mestome bundles of the prophyllum, though less 
completely developed; and the same result was obtained as 
before when treating the sections with concentrated sulfuric acid, 
that is, the outer sheath dissolved at once, together with the 
adjoining cells of the collenchyma, from which it must be 
