358 The Botanical Gazette. [June 
is especially noticeable when we examine the median part of 
the leaf (fig. 1). There are two midribs, one above the other, 
of which that nearest the inferior face is the largest (a, fig. 
1). Besides these the section contains eight other ribs, of 
which those of the superior face are the smallest. We have, 
however, examined leaves of other specimens in which the 
median part of the blade contained no less than twenty-four 
mestome bundles, two of which were imbedded in the color- 
less parenchyma. 
Turning to the lateral parts of the blade (fig. 2), we observe 
a similar difference in the development of the mestome bun- 
dles and by comparing them with those of the keel, we may 
distinguish four different degrees of development. The mid- 
rib of the inferior face represents the largest mestome bundle. 
It is surrounded by colorless parenchyma, of which the inner 
layer forms a sheath all around the bundle, bordering on a 
thick-walled and perfectly closed mestome sheath. The lep- 
_ tome and the hadromeare well differentiated and separated from 
each other by a small layer of thick walled mestome paren- 
chyma. This mestome bundle is not in connection with any 
parenchyma. 
The mestome bundles of second degree (4, fig. 1) are repre- 
sented not only in the median but also in the lateral parts of 
their smaller size and by the fact that the parenchyma sheath 
is here interrupted by the stereome on the inferior face of the 
bundle. The Superior face, on the contrary, shows a group 
