352 Dr. A. Eraun on the Vegetable Individual. 



the formation of the stalk ; and its rudiment is contemporaneous 

 with the first stages of the formation of tissue in the punctum 

 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 recognized even in the 

 developed state, in those plants w'hose foliaceous pulvini are di- 

 stinctly marked, as e. g. in many Ferns, most acerose plants, iri 

 Cacti, and particularly in Nijmphcea and Victoria, where the pul- 

 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 deve- 

 lopment they always succeed the leaves ; and even at a much later 

 period, when the leaves have been long cast off, shoots may 

 originate 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 develope very 

 late or not at all, in the form of a circular and slightly promi- 

 nent gibbosity, 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 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 subsequent internal and external conformation; for it not 

 only developes leaves upon its surface, and this too with an in- 

 dependent commencement of its phyllotaxis, but even in its 

 interior the first system of vascular fibres seems to be formed in- 

 dependently of that of the main axis ; as originally it lies upon 

 it, and afterwards becomes intimately blended with it by later 

 layers of tissue. Notwithstanding the intimacy with which later 

 formations of woody tissue unite branch and stem, still, accord- 

 ing to Unger's investigations, no immediate influence is exerted 

 by the branch upon the conformation of the stem, since the stem 



