422, VEGETABLE PHYSIOLOGY 
respects. This is known as gemmation or budding. It may 
go on so rapidly that the new cell in turn may put out a 
bud of its own before it is cut off from its parent, and in 
that way chains of cells may be produced (fig. 162). 
A more general method of the division of the cell is 
of a highly complicated character, and is preceded by 
an elaborate division of its nucleus. This structure we 
have seen consists essentially of a delicate network of 
fibrils of chromatin embedded in a hyaline substance, the 
whole being surrounded by a more or less well-defined out- 
line derived from the cell-protoplasm, and known as the 
nuclear membrane. Associated with it in some cases are 
ie} 
Gm, & Os OS as 
gee ne § Se age se 8 
a b 
Fie. 162.—SaccHAROMYCES CEREVISLH, OR YEAST-PLANT, AS DEVELOPED 
DURING THE PROCESS OF FERMENTATION. X 300. 
a, b, c, d, successive stages of cell-multiplication. 
two small centrospheres. The process of division, which is 
known as Karyokinesis, or Mitosis, begins by the network 
of fibrils becoming coarser and gradually separating to 
form a long coiled fibre. The nucleoli disappear and the 
nuclear membrane ceases to be distinguishable. At the 
same time, in those cases in which centrospheres have 
been seen, they shift their position and come to lie on opposite 
sides of the nucleus at some little distance from it. The 
long coiled fibre of chromatin breaks up into a number of 
pieces, often V-shaped, which point towards the centre of 
the nucleus. The number of these varies in different cases, 
but is constant in the successive divisions of an individual. 
These pieces of the fibre are known as chromosomes. The 
chromatin in them is broken up into small portions which 
are separated from each other by smaller films of unstain- 
able substance. 
