Development, and Structure of the Vegetable Cell. 125 
which are directed towards the extremities of the mother cell ; 
between these and the septum produced by the mutually opposed 
membranes of their primary cells a system of mucilaginous 
filaments makes its appearance in the direction of their radu, 
indicating the formation in them of secretion-cells similar to those 
of the mother cell. These cells may be brought into sight by 
the action of dilute solution of tannin and of some other 
endosmotic fluids. 
Upon the different directions of growth of the two daughter 
cells (2. e. whether they extend themselves more in the first or 
the second of the indicated directions) depends both the greater or 
~ less removal of the nuclei of the daughter cells from the median 
line of the mother cell at the appearance of the septum, and also 
the modifications in the mode in which this septum becomes 
visible at the surface of the joint-cell. 
If the daughter cells at first follow especially the first indi- 
eated direction of growth, 7. e. if they increase most in breadth, 
their central flattened walls attain the surface of the joint-cell, 
whilsttheir free peripheral portions directed towards the extre- 
mities of the mother cell scarcely form a hemispherical surface. 
These mutually flattened walls appear, on coming into contact 
with the wall of the mother cell, as the new septum. 
The membranes of the secondary cell of the joint-cell, as also 
the chlorophyli-sac applied to their inner surface, cover the 
outer circumference of the septum, and even conceal it when 
a starch-vesicle or an opake chlorophyil-vesicle lies. immediately 
upon it. 
If, however, the daughter cells extend at first less in this 
direction than in the direction of their length, so that their free 
surface, instead of becoming hemispherical, approaches more or 
less to a spherical form, those phenomena occur which have 
hitherto been usually observed and described as the normal 
process. 
In this state (in which the small secretion-vesicles surround- 
ing the cell-nucleus are in process of absorption, and therefore 
collapse readily by any diosmotic process) the secondary ‘cell, 
with the adherent chlorophyll-sacs, readily sinks down upon the 
more or less spherical daughter cells, which, however, always 
have a part of their surface flattened against each other, forming 
the depression which is frequently observed and regarded as a 
preliminary of the septum-formation. 
That this fold-like depression is not essentially connected 
with the formation of the septum, but that it occurs only in a 
less complete and not perfectly regular course of development, 
appears from the circumstance that it is met with chiefly in cul- 
tivated plants, or in those which have grown in their natural 
