482 Prof. H. Karsten on the Formation, 
by the different size of these cells in different mother cells, even 
in the same anther. By the agency of diosmotic fluids, the 
secondary pollen-cell detaches itself from the primary cell, and — 
contracts into an irregularly shaped or lobed body upon the 
granularly cellular contents. 
It is at a somewhat later stage of development that these 
large mother cells of the pollen-cells detach themselves singly 
from their compartment (fig. 9). The central nucleus is then 
still recognizable; but its nuclear corpuscle is seen no longer, 
or with difficulty. The nucleus is situated between four deli- 
cate-walled cells, the peripheral portions of the membranes of 
which are closely applied to the mother cell. 
The membrane of the mother cell is more thickened, rather 
unequally and in lamine; at that part above the septal wall of 
the two endogenous cells it is rather thicker, and at a later 
period its thickness becomes still more decidedly pronounced. 
By means of solutions of salts, of sugar, &c., it is possible, 
even at this stage of development, to separate the contents of 
the daughter cells from the still delicate primary membrane. 
The contents of each cell separately form a more or less spherical 
and smooth mass, whilst the four together constitute a lobed 
body seen within the centre of the mother-cell, which is divided 
into compartments by very delicate membranes. These four 
daughter cells behave, when treated with reagents, in an appa- 
rently similar or identical manner with those of Cladophora 
already described. Here also the four daughter cells coherent 
in the centre may be isolated by the partial solution of their 
primary cell-walls by reagents; and if the mother cells were in- 
jured by cutting, they are, although but rarely, pressed out 
from it, nearly in the form in which Mohl represented this 
‘Vegetable Cell’ (taf. 1. fig. 10). 
The granular contents of the secondary pollen mother cells 
external to the daughter cells either vanish entirely, or a mu- 
cilaginous-looking material appears in their stead around these 
cells, in which case the delicate envelopes of the daughter cells 
look like the inner contour of a thick-walled cell. In conse- — 
quence of these changes the pollen mother cell acquires a great 
similarity to the next phase of development, in which, instead of — 
the central nucleus, a gelatinous mass occupies the centre of the 
cell betwixt the four daughter cells (fig. 11). This breaking-up 
of the regenerating nucleus of the cell (nuclear cell) is a sign of — 
the termination of the individual development of the mother 
cell. The contiguous walls interposed between the four endo- 
genous and much-distended cells form between them apparently 
simple and very delicate laminz, which appear to subdivide the 
cavity of the mother cell then filled with opalescent mucous fluid. 
