CHAP. II. 
LEAF. 
89 
1. Of the Leaf. 
44 45 46" 4 7 
48 49 
The leaf is an expansion of the bark at the base of a leaf- 
bud, prior to which it is developed. In most plants it con- 
sists of cellular tissue filling up the interstices of a net-work 
of fibres that proceed from the stem, and ultimately separating 
from the bark by an articulation ; in many Monocotyledonous 
plants. Ferns, and Mosses, no articulation exists, and the base 
of the leaf only separates from its parent stem by rotting 
away. 
This difference of organisation has given rise to a distinc- 
tion, on the part of Oken, between the articulated leaves of 
Dicotyledons and the inarticulated leaves of Monocotyledons 
and Acotyledons: the former he calls true leaves, and dis- 
tinguishes by the name of Lauh ; the latter he considers 
foliaceous dilatations of the stem, analogous to leaves, and 
calls Blatt 
A leaf consists of two parts ; namely, its stalk, which is 
called the stalk or petiole (fig. 45. a), and its expanded surface, 
which is called the blade or lamina (fig, 45. c, Z>, d) : in ordi- 
nary language the latter term is not employed, but in very 
precise descriptions it is indispensable. 
The point where the base of the upper side of a leaf joins 
the stem is called the axil ; any thing which arises out of that 
point is said to be axillary. If a branch or other process 
proceeds from above the axil, it is called supra-axillary ; if 
from below it, infra-axillary. 
