280 
only the upper surface of the leaf is visible from without, the lower 
surface lining the cavity thus formed. The groove on the under 
surface of the leaf is the narrow slit-like opening left between the 
rolled-under blades through which the lower surface of the leaf has 
direct communication with the air. The anatomy is in general 
that of the typical dicotyledonous leaf, but with some peculiarities 
to be described in detail. 3 
Beginning with the upper epidermis (Fig. V.), the enormous 
size of its cells and the extreme thickness of the outer wall are 
first noticed. By actual measurement this outer epidermal wall, 
in some instances, equals one-fifth of the entire distance from the 
upper to the under surface of the leaf. The epidermal cells are. 
further distinguished (Fig. V.) by a thickening of the walls which 
projects into and partially fills the lumen. These projections are 
sometimes in the form of irregular masses, but oftener the walls — 
are thickened regularly, some time nearly filling the lumen. In 
all cases these thickenings, together with all the walls of the epr 
dermal cells, except the sharply defined outer layer’ of the uppef 
wall, respond to the tests for cellulose. The outer layer shows 4 
cutin reaction. The mesophyll tissue consists of two layers: of 
palisade cells and spongy tissue below of irregular branching 
parenchymatic cells with very large intercellular spaces. ae 
lower epidermis, unlike the upper, consists of cells of ordinary 
size, and these are interrupted by numerous raised stomata. 
The entire lower surface of the leaf is thickly covered with 
hairs of two kinds—long, one-celled, thick-walled hairs, and three- 
five-celled capitate glands. The simple hairs predominate. The 
vascular system is simple, the shape of the leaf being such as 
to require but little supporting tissue. “At regular intervals 
lateral bundles branch from the stout midrib, and there is 4 mere 
trace of bundles forming the net-veining of the dicotyledonous 
Va 
type. An entire absence of bast cells is a peculiarity of thes¢ — 
bundles, a circumstance not remarkable in a leaf which needs 5° 
little strengthening element. An endodermis of somewhat thick? 4 
walled cells encloses the whole vascular system, separating the ie 
bundles from the surrounding tissues. see 
The leaf of C. Conradii is smaller and is minutely denticulate 
on the apparent margins, but otherwise it has the same outwa ia 
