184 Mottier.—Nuclear and Cell Division 
down as a • single membrane, which afterwards splits, or 
whether two membranes are formed from the beginning, is 
difficult to decide. I am inclined to think that it is laid 
down as a double plasma-membrane, since evidence of the 
process of actual splitting was not seen, and immediately 
the cell-plate is formed, plasmolysis shows that each proto¬ 
plast has its own plasma-membrane. 
Concerning the form in which the cell-plate substance is 
deposited, there may be much diversity of opinion. In the 
higher plants, we may contend with Strasburger (’ 98 , p. 514), 
that the plasma-membrane is formed by the lateral fusion 
of the thickened connecting fibres, when it would consist 
of many very small kinoplasmic rods ; or we may assume 
that the cell-plate substance is deposited as a homogeneous 
fluid. Both in the higher plants and in Dictyota there is 
much that supports the second of these assumptions. 
That the cell-plate in the higher plants is formed by the 
lateral union or fusion of the thickened connecting fibres 
may be seriously questioned, for in some cases these fibres 
do not thicken very appreciably in the equatorial region, nor 
do they lie sufficiently close to one another to enable the 
slightly thickened middle parts to meet and fuse laterally. 
I refer, for example, to the formation of the egg-cell in the 
embryo-sac of Lilium Martagon (Mottier, ’ 98 , Taf. Ill, 
Fig. 21). There the connecting fibres are only very slightly 
thickened in the region of the cell-plate, and they are too 
far apart to lead one to believe that the plasma-membrane 
is the result of the lateral fusion of the slight equatorial 
thickenings of these fibres. In this and in similar cases 
among higher plants, the conclusion seems justifiable that the 
cell-plate is formed by homogeneous plasma which is con¬ 
veyed to the cell-plate region and deposited there by the 
connecting fibres. 
In Dictyota there are no connecting fibres, neither does 
the cell-plate consist, at first, of a row of granules which 
* split later to form the two plasma-membranes as described 
by Strasburger (’ 97 , p. 359) for Fucas. The cell-plate does 
