58 
ORGANOGRAPHY. 
BOOK I. 
petiole, the leaf itself, have all been remarked producing 
them. On the leaf they usually proceed from the margin, as 
in Malaxis paludosa, where they form minute granulations, 
first determined to be buds by Henslow, or as in Bryophyl- 
lum calycinum and Tellima grandiflora ; but they have been 
seen by Turpin proceeding from the surface of the leaf of 
Ornithogalum. (Fig. 18.) 
We are wholly unacquainted with the cause of the forma- 
tion of leaf-buds ; all we know is, that they proceed exclu- 
sively 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 bladder 
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 they 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 grow freely, 
and after a time will emit small roots from just above its 
union with the stock ; at the time when these little roots are 
formed, let the shoot be cut back to within a short dis- 
tance of the stock, and the little roots will then, in conse- 
quence of the great impulsion of sap into them, become 
branches emitting leaves. 
