CHAP. II. 
AXIS. 
Ill 
a poet, is now universally acknowledged to be an indisputable 
truth. It may, however, be remarked, that when those who 
first seized upon the important but neglected facts out of 
which this theory has been constructed, asserted that all ap- 
pendages of the axis of a plant are metamorphosed leaves, 
more was stated than the evidence at that time would justify; 
for we cannot say that an organ is a metamorphosed leaf, 
when, in point of fact, it has never been a leaf. What was 
meant, and that which is supported by the most conclusive 
evidence, is, that every appendage of the axis is originally 
constructed of the same elements, arranged upon a common 
plan, and varying in their manner of developement, not on 
account of any original difference in structure, but on account 
of especial, local, and predisposing causes : of this the leaf 
is taken as the type, because it is the organ which is most 
usually the result of the developement of those elements, — 
is that to which the other organs generally revert, when, from 
any accidental disturbing cause, they do not sustain the ap- 
pearance to which they were originally predisposed, ■ — and 
moreover, is that in which we have the most complete type of 
organisation. 
It is not my intention just now to enter into separate 
discussion of this doctrine; proof of it will be more con- 
veniently adduced as the different modifications of the ap- 
pendages of the axis come respectively under consideration. 
The leaf, as the first that is formed, the most perfect of them 
all, and that which is most constantly present, is properly 
considered the type from which all the others are deviations, 
and is the part with the structure of which it is first necessary 
to become acquainted. 
