CELL-DIVISION. 31 
The question now remains whether in all micro- and macro-spore 
mother-cells of the higher plants a double longitudinal splitting of the 
chromatin takes place during the first mitosis and how prevalent such 
a phenomenon is in both plants and animals. 
In those plants in which the daughter nucleus passes into the struc- 
ture of the complete resting stage, it is certainly difficult to understand 
the significance of the double longitudinal splitting of the chromosomes 
in the first division. 
CELL-DIVISION. 
THE TYPE OF THE HIGHER PLANTS. 
Modern research has established the very important fact that new 
cells are formed from uninucleate or multinucleate mother-cells accord- 
ing to different methods, depending largely upon the manner in which 
the new plasma membranes differentiating the cells are formed. 
(1.) Among the higher plants, and some Thallophyta as well, in 
which cell-division is generally intimately associated with nuclear 
division, the new plasma membrane or membranes are laid down 
through the instrumentality of kinoplasmic connecting fibers, extending 
between the nuclei concerned. 
(2.) In the ascus of certain Ascomycetes, where the new cells 
(spores) are carved out of a common nucleated mass of cytoplasm or 
mother-cell, the plasma membrane is also formed by kinoplasmic 
fibers, but these are polar radiations and not connecting fibers. The 
entire plasma membrane of such cells is new, that of the mother-cell 
taking no part in the process. This is typical and real free cell- 
formation. 
(3-) Another form of cell-division is found among the AZyxomycetes 
and certain Phycomycetes, in which the new plasma membranes arise 
by a process of progressive cleavage, beginning at the surface, with or 
without any connection with, or aid of, vacuoles. Kinoplasmic con- 
necting fibers or radiations are in no way connected with this process. 
This type we may know as cel/-cleavage. It resembles the cleavage of 
animal cells more closely than do the other processes of cell-formation 
in plants. 
(4.) There is yet another method of cell-formation typified by 
Dictyota and Stypocaulon among the brown algz, in which the new 
plasma membrane seems to be a direct transformation of the meshes 
or threadwork of the cytoplasm. It is not a cleavage like the last 
mentioned, nor are any connecting fibers present to take part in the 
