IO Raymond John Pool 
peripheral layer of protoplasm. This fact may be rather surpris- 
ing to those who have held the view that trichome cells and the 
cells of the epidermis are inactive and that they contain only air. 
The above facts indicate that such cells are not so “dead” as has 
been supposed. Indeed, most of the plants described in this paper 
showed the epidermal nuclei to be almost always present ; in many 
cells it was very large and conspicuous, 
Leaves from plants in the drier situations, for instance from a 
holard of 8 to 12 per cent, regularly show in addition to the lanate 
surface a well-defined cuticle (plate I, figs. 1 and 2). The leaf 
is greatly pitted so that in a transverse section the epidermis ap- 
pears as an undulating chain of cells. In many of these pits are 
found peculiar multicellular epidermal glands which will be de- 
scribed below. Stomata are about equally distributed over the 
upper and lower surfaces. The chlorenchyma_ is composed of 
four rows of irregular, prolate palisade cells closely packed to- 
gether, with very small intercellular air spaces. Two rows of 
these cells occur on each side of a median band of globose water 
storage cells. In the sections from the drier situations (plate I, 
fig. 1) this band is made up of two to three rows of cells with a 
close sheath about the vascular bundles. In these forms the cells 
comprising the bundle storage sheath are often filled with a 
mucilaginous or viscid cell sap. In no cases do the storage cells 
contain chloroplasts, although these cells do originate from 
chlorophyll-bearing cells. 
The relative development of this median storage tissue shows 
some rather slight variation in the shade forms and in those grow- 
ing under more moist conditions. Figure 2 was made from a 
plant growing in a holard of 18 per cent. Here the storage region 
is reduced to a single plate of cells, and the bundle sheath never 
contains mucilaginous material. Otherwise the leaf is the same. 
Figure 3, plate I, shows a leaf section from deep within the same 
plant from which figure 2, plate I, was made. This leaf grew 
under a lower light intensity than the other. The structural dif- 
ferences noted are that, first of all, the leaf is much broader and 
thinner. The epidermal hairs are more scattered, there is no 
cuticle at all, storage cells are not so numerous, and the two inner 
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