The Vegetable Individual in its relation to Species. 199 
vegetationis. A leaf can never be formed at a later period from 
the developed axis. It is a necessary consequence of the manner 
in which the leaf originates, that an absolute dividing line cannot 
be drawn between leaf and axis ; for the subsequent position of 
the leaves upon the organism affords no standard of appreciation, 
especially as most of them do not mark the basis of the leaf, which 
loses itself in the axis. Earlier, before the extension of the axis 
begins, the rudiments of the leaves are always closely pressed to- 
gether, so that they appear as a peripherical development of the 
axis itself, occupying the whole upper surface, and dividing it 
into clearly defined planes, which may be recognised even in the 
eveloped state, in those plants whose foliaceous pulvini are dis- 
tinctly marked, as e. g. in many Ferns, most acerose plants, in 
Cacti, and particularly in Nymphea and Victoria where the pui- 
vini may be distinguished even in the interior of the axis. ‘The 
primitive vascular system of the axis enters directly into the 
leaves, and ramifies there ; while the woody layers of the stem, 
which are found later, have no connexion with the leaves. With 
branches the case is totally different. In their origin and devel- 
opment they always succeed the leaves ; and even at a much later 
period, when the leaves have been long cast off, shoots may ori- 
ginate in places where, at an earlier period, no trace of a rameal 
rudiment, or of an eye, was to be found. If we now consider 
the axillary shoots,—i. e. those branches whose position is pre- 
determined by the situation of the leaves,—at an early period we 
shall find their rudiments, even though they develop very late or 
not at all, in the form of a circular and slightly prominent gibbos- 
ity, which may be compared with the apex of the axis; or rather, 
it is an accessory punctum vegetationis forming near the apex. 
The circumstance of the epidermis of the axillary shoot’s being 
a continuation of that of the stem, is explained by the early date 
at which it originates ; for this takes place at a time when the 
surface of the axis has not yet lost its flexibility. The eye is 
shown to be an independent centre of vegetation by its subse- 
quent internal and external conformation ; for it not only devel- 
* Unger : Ueber den Bau des Dicotyledonen-Stammes (1840), p. 65, et 66. 
