PHYTOGENESIS. 257 
I return, after this digression, to my subject. So far I be- 
lieve I have demonstrated tolerably conclusively, and in accord- 
ance with nature, that the entire growth of the plant! consists 
only of a formation of cells within cells. Let us now pass on 
to the root. I can contribute but very little to the explana- 
tion of this part of the subject; for I have not as yet succeeded 
in arriving at any satisfactory result, from the somewhat limited 
researches which I have instituted ; for instance, I have been 
altogether unsuccessful in deciding the question as to whether 
a fluid is secreted at the extremity of the radicle, in which 
new cells are developed. On the other hand, it is certain that 
there exists in the extremity of the root a concavo-convex 
mass (a meniscus) of cellular tissue, in which the process of 
cell-formation takes place in the same manner as in the parts 
of the plants which grow in the ascending direction. <A chief 
cause of the elongation of the root consequently consists m 
this,—that new cells are continually formed in the interior of 
the existing cells, on the convex side of that mass of cells, 
while on the concave side, the cells already formed expand 
simultaneously, and chiefly indeed in the longitudinal direction, 
and in this way constantly push the extremity of the root 
before them. 
The third case, the formation of the accidental organs of the 
plant, I must entirely pass over, as I am altogether unpro- 
vided with any personal observations upon the subject. Pro- 
bably, however, the process here is the same as in the previous 
cases, for Meyen (Physiologie, vol. i, p. 209) observed the cell- 
nuclei in germinating tubers of Orchidee. Analogy also leads to 
a similar conclusion, since all these parts are nothing more than 
morphological modifications of organs which have been already 
treated of in this memoir. ‘The fourth pomt, however, still 
remains for discussion, namely, the increase in thickness of 
plants which form woody stems (Dicotyledons). The origin and 
signification of cambium is the nut on which so many young 
phytologists have already broken their milk-teeth, the Gordian 
knot which so many botanical Alexanders have cut instead of 
untying, and the enigma, for the solution of which almost all 
the Coryphei of our science have laboured with more or less 
' I beg to observe, that generally throughout the entire memoir phenogamous 
plants only are referred to. 
17 
