96 MOHL ON THE STRUCTURE OF THE VEGETABLE CELL. 
cambium layer, places where the number of elementary organs 
continually augments without any interruption of the continuity 
of the tissue, or any spot where a new elementary organ could 
insinuate itself between those already formed, being discoverable, 
two modifications only of the process of cell-generation are pro- 
bable.—the division of the older cells by the formation of a sep- 
tum, or the formation of cells within cells. In each of these 
young cells, without exception, a primordial utricle may be found ; 
the origin of this, therefore, is at least contemporary with the 
formation of the cell itself. If it could be positively ascertained, 
that in cells which are in the act of increase two primordial utri- 
cles exist near together before the septum is developed between 
them, it would be decided, as far as relates to the cambium layer 
and the apex of stems and roots, that here the formation of the 
primordial utricle precedes the formation of the cell, and the 
name I have applied to it would be justified. I believe that I 
have actually observed this process repeatedly, especially in the 
cambium layer of Pinus sylvestris, Sambucus Ebulus, Asclepias 
syriaca, in the bark cells of Rhus typhinum, in a young leaf of a 
Sempervivum, and in the apex of the stem of Euphorbia Cuput 
meduse ; since, however, the transverse septa, at their first ap- 
pearance are particularly delicate, and it being very possible that 
the deficiency of the transverse wall between two primary cells 
was only apparent and consequent on a rupture of it, I dare not 
venture to publish these observations as absolute facts, although 
I took every care to remove any sources of illusion. Since each 
young cell contains a primordial utricle, either this must be ab- 
sorbed before the increase of the cell commences, to make room 
for two new ones originating in its place, or the old primordial 
utricle must separate by constriction into two; I could not suc- 
ceed in ascertaining the most minute details by observation, but 
the former is the more probable, as the formation of the primor- 
dial utricle in vascular plants is always connected with the for- 
mation of the nucleus*. Ungert+ first announced that the 
* The division of the cells which takes place in Confervze is probably a totally 
different process from the multiplication of cells in vascular plants; at least I find 
no nucleus in the true Conferve, and have never seen, in Phanerogamous plants, : 
a constriction of the primordial utricle by a septum growing from without in- 
wards, similar to that which occurs in the Conferve, in which the primordial 
utricle continues, without interruption and without a transverse septum, through 
the constricted part until on perfect strangulation it separates into two distinct 
utricles. 
{ Ueber die Genesis der Spiralgefasse, Linnea xv. 385. 
