CHAP. II. 
STEM. 
75 
tliey are placed in their normal station, and they call all 
others latent or adventitious. The latter have been found in 
almost every part of plants ; the roots, the internodes, the 
petiole, the leaf itself, have all been remarked producing 
them. On the leaf they usually proceed from the margin, as 
in INIalaxis paludosa, where they form minute granulations, 
first determined to be buds by Henslow, or as in Bryophyllum 
calycinum and Tellima grandiflora ; but they have been seen 
by Turpin (fig. 19.) proceeding from the surface of the leaf of 
Ornithogalum. (Fig. 20. represents a vertical section of one 
of these buds.) 
19 
We are unacquainted with the cause of the formation of 
leaf-buds ; all we know is, that they proceed exclusively from 
cellular tissue ; and if produced on the stem, from the mouths 
of medullary rays. It would seem as if certain unknown forces 
were occasionally so exerted upon a vesicle of cellular tissue 
as to stimulate it into a preternatural degree of activity, the 
result of which is the production of vessels, and the formation 
of a nucleus having the power of lengthening. There is, 
indeed, an opinion, which I believe is that of Mr. Knight, 
that the sap itself can at any time generate buds without any 
previously formed rudiment ; and that buds depend, not upon 
a specific alteration of the arrangement of the vascular system, 
called into action by particular circumstances, but upon a 
state of the sap favourable to their creation. In proof of this 
it has been said, that if a bud of the Prunus Pseudo-cerasus, 
or Chinese Cherry, be inserted upon a cherry stock, it will 
