428 Prof. H. Karsten on the Formation, 
before one of the two cells has extended itself more or Jess com= 
pletely from the cylindrical cavity of the mother cell in the form 
of a branch. It might be imagined that it is so forced out by 
the contemporaneous predominant growth of the sister cell. 
This regular course of branch-formation is not, however, always 
thoroughly carried out ; the lower extremity of the branch-cell 
frequently remains within the mother cell, and aids to form 
along with its sister cell a septum in the form of an oblique or 
horizontal thickened lamina. 
The externally visible phenomena which accompany the pro- 
cesses of normal septum-formation in C. glomerata may readily 
mislead one into regarding the explanation given of them by 
Mohl as the natural one. ’ 
Having, however, ascertained that in the joint-cells of C.glome- 
rata there is generally concealed beneath the superficial layer of 
secretion-cells a complete tissue of endogenous cell-systems—a 
tissue which certainly does not cohere, like the cellular tissue of 
more highly organized plants, by intercellular substance, or at 
least not by such as is insoluble in water and which consists, 
not of persistent tissue-cells, but almost entirely of transitory 
secretion-cells (for large mother cells may be seen, filled with cells 
of nearly half the size of a joint-cell, to swell forth from the cut 
joint of the Conferva),—having ascertained that the flat horizontal 
septum produced by the mutual apposition of these endogenous _ 
cells occurs already formed (fig. 46 g) in the secondary cell be- 
fore this has become thickened, and having been able in certain 
cases, by means of endosmotie fluids, to divide this septum and 
to recognize its composition out of parts of two neighbouring 
cells (fig. 46 x),—having, further, even in C. glomerata, excep- 
tionally seen septa normally formed by the mutual apposition 
of two cells originally separate (p. 419, fig. 32) and even belong- 
ing to different generations,—we shall feel called upon to submit 
the normal process of septum-formation in this plant to another 
examination in order to try to refer it to the general law of cell- 
formation. 
Fig. 40 a (Pl. VI.) exhibits the phenomenon first witnessed 
by Dumortier (Nova Act. Leop.-Carol. 1832) and described in 
detail by Mohl, which is regarded by him and his followers as a 
folding of the walls of the joint-cells of C. glomerata in process 
of multiplication, and as the type of “ cell-formation by fission.” 
Mohl (Vermischte Schriften, 1845, p. 623; Veget. Zell. 1851, 
p- 212; Botanische Zeitung, 1855, p. 689) supposed that the in- 
ternal surface of the secondary cell (primordial layer) is overlaid 
with a granular mucoid protoplasm, the chlorophyll-layer, which 
gives way at the same time or nearly so that the involution (fold) 
of the walls, formed by the primordial layer and the youngest 
=r. 
Pine ke ee 
