THE LIVING CELL 45 
There are five chief modes of AsExuaL REPRODUCTION, Viz.: 
Fission or Binary Division, Gemmation, Free Cell Formation, Rejuve- 
nescence and Vegetative Multiplication. 
Fisston.—This is the separation of a cell into two equal halves, 
each of which may grow to the size of the original parent cell 
from which it was derived. Fission is seen in the reproduction 
of bacteria, growth of many algze and the formation of tissues of 
higher plants. 
In fission or binary division, as the process is frequently called, 
there may occur (1) a division of the cell by means of a cell 
plate of the nature of a plasma membrane formed by the shrink- 
_ age of the spindle fibers to the equator of the cell during mitosis. 
This cell plate splits, forming two plasma membranes, between 
which the cell walls separating the daughter cell are laid down, 
or (2) a division by constriction. In the latter method, as seen 
in some of the algae, the cytoplasm becomes constricted or pushed 
away from the wall of the cell at a point midway between the 
ends of the cell and at this constriction the cytoplasm lays down 
a transverse wall of ring-like form. As the constriction deepens, 
the new transverse wall broadens until, when division is com- 
pleted, it forms a completely closed circular disk. 
Gremmation or Buppinc.—This is the method of reproduction 
common among yeasts. (See Fig. 284.) The cell forms a pro- 
tuberance called a bud which increases in size until it equals the 
size of the cell which formed it and then becomes detached, 
although frequently not until it has developed other buds and 
these still others. 
Free Ceti ForMATION.—This is a type of reproduction 
which consists of the cutting out of cells within the common 
cytoplasm of a cell by the activity of spindle fibers attached to 
the nuclei. These curve around the nuclei and form plasma 
membranes each of which lays down a cell wall. Seen in the 
formation of ascospores within the ascus of Ascomycetes. 
REJUVENESCENCE Or ZOOSPORE ForMATION.—In this mode of 
reproduction the protoplasm of the cell becomes rounded out, 
escapes by rupture of the cell wall, forms cilia and moves about 
as a zodspore. Later it looses its cilia, develops a cell wall and 
passes into a resting condition. Under favorable circumstances 
