276 Prof. H. Karsten on the Formation, 
their interior than the ligneous cells themselves, and this even 
without any wounding of the vessels. I removed a ring of bark 
from a twig of Salix babylonica, and found, in the following 
ear, all the vessels of the peripheral lamina of the wood entirely 
filled with cells, whilst the woody cells, on the contrary, remained 
unaltered. The cells thus formed in the interior of vessels 
may, under certain circumstances, be transformed into new 
vascular cells, after the thickened wall of the parent vessel has 
been absorbed, and may contribute to the lengthening of the 
original vessel—a case which I have described and figured, in 
my researches on the organs of vegetation of the Palms, with 
regard to Lycopodium Spring (pp. 120 & 163, pl. 9. fig. 15), 
the vascular bundle alone having been developed into a root- 
fibre. 
By the maceration in solution of potash of the cells which 
make their appearance in the vessels during the formation of 
callus, it may also be demonstrated that they are not produced 
by constriction, but as free vesicles in the fluid contents of the 
cells and vessels, although the observation of the moment of 
their production presents exactly the same difficulties here as in 
the case of the suberous tissue. 
§ II. On Cell-formation in Edogonium. 
New joint-cells by evolution of endogenous cells.—Absorption of the 
secretions of the mother cell, with contemporary formation in the 
daughter cells.—Absorption of the nuclear cell.—Development and 
growth of the nuclear cell.—Cellular contents of the developed joint- 
cells.—Downward-prolonged annular folds of the primary cell-wall.— 
Bary’s globules of decomposition contain animal parasites. 
The peculiar behaviour of the mother cell, in the several spe- 
cies of the genus Cidogonium, during the formation of daughter 
cells, has been most fully elucidated by Bary (Schriften der 
Senkenberg’schen Gesellschaft, Band i. 1854-55). From his 
investigations we know that, in the course of elongation of a 
joint-cell, the primary cell-wall forms at its upper part an in- 
growing annular fold, and that this fold, after the membranous 
envelope covering the mother cells is torn through, suddenly 
extrudes itself, and thus causes a considerable elongation of the 
joint-cell. | 
The internal structure of the @dogonium-cells and the mode of 
multiplication of the joint-cells have, however, not yet been ascer- 
tained. The latter is, as usual, represented to be a consequence 
of the formation of septa by constriction of the walls; and, ac- 
cording to Bary, the septum is formed in the suddenly extended 
cell within a colourless layer which divides the green mass of — 
contents into two parts, and not until this layer has issued from 
