The Morphology of Ruppia Maritima. 94 
These reactions confirm Sauvageau’s assertion that these cells are 
tanniferous. As is well known, tannin is a common byproduct 
in plants, and in this case is possibly deposited in special cells on 
account of the difficulty of its diffusion through the epidermis. That 
these tanniferous cells should be more abundant toward the base of 
the leaf is natural, for it would be more economical for the plant 
to devote as many as possible of the cells in the upper part of 
the leaf to photosynthesis. 
(4) Absence of Stomata. 
Another peculiarity of the epidermis is the absence of stomata, 
which will be discussed later (p. 118). 
b. Subepidermal Layer. 
Below the epidermis, at all parts of the leaf, is a distinct layer 
one cell thick, which I have termed the subepidermal layer (PI. VIL, 
fig. 43), composed of cells about twice 
the width, tangentially, of those of the 
epidermis; and longitudinally, i. e. running 
the length of the leaf, many times longer 
than the epidermal cells (Text-fig. 13). 
This layer contains a few chloroplasts 
(cf. Sauvageau, 1891, II, p. 293). 
c. Vascular System. 
The vascular system of the leaf is ex- 
tremely simple. Three strands of con- 
ducting tissue are present—one large 
axial and two small marginal. 
(1) Course of Vascular Bundles. 
These three vascular strands enter the me ; 
Cae 5 Figure 13.— Portion of sub- 
leaf separately at its insertion on the stem. — epidermal layer of leaf 
The axial bundle maintains a median po- _ blade, showing a few chlo- 
sition and extends to very near the tip eee. Lee 
ongitudinal section cut 
Brethe leaf (Pl: V1, figs. 26,°30; Pl. VU, trom living leaf. >< 335. 
fig. 43); the two lateral bundles enter 
one on each side of this axial bundle, and throughout their extent 
run parallel to it (Pl. VII, fig. 43, 76). 
In the region of the sheaths each of these lateral bundles runs 
along the edges of the leaf proper, just at its line of junction with 
the sheaths, and above the leaf sheaths they retain this marginal 
position. I can confirm Sauvageau’s (1891, II, p. 210) observation that 
they do not unite with the median bundle near the apex of the 
leaf, but disappear—according to my preparations, about 10 mm. 
from the apex. 
Trans. Conn. Acap., Vol. XIV. 7 DercempBer, 1908. 

