THE LIVING CELL 47 
female sexual cell, is larger and passive. This process is seen 
among the higher and many of the lower plants. 
InprreEcT Nuciear Drvision (Mitosis oR KARYOKINESIS) 
This is the general method of division seen in the formation 
of tissues of higher plants. 
The process begins in the nucleus and ends with the forma- 
tion of a cell wall dividing the new-formed cells. 
When we examine a cell in its resting stage, we find the nucleus 
more or less spherical in shape, surrounded by a nuclear membrane 
and containing a nuclear network, nuclear sap and one or more 
nucleoli. The nuclear network consists of a colorless network of 
linin adhering to which are numerous minute granules called 
chromatin which take the stain of a basic dye. Surrounding the 
nucleus is the cytoplasm. 
As the cell commences to divide, the nucleus elongates and 
the linin threads of the nuclear reticulum shorten, drawing the 
chromatin granules together into a thickened, twisted, chromatic 
thread called the .spireme. This thread splits transversely and 
thus becomes divided into a number of rods termed chromosomes. 
Each of these then splits into two longitudinal halves that may 
be termed the daughter-chromosomes. They lie within the nuclear 
cavity united by delicate threads. There now begins a phe- 
nomenon concerned with the cytoplasm which is primarily a 
process of spindle formation. The granular cytoplasm accumu- 
lates at the poles of the elongated nucleus, forming the cytoplasmic 
caps. Presently it begins. to show a fibrillar structure, the 
threads extending outward around the periphery of the nucleus 
forming an umbrella-like arrangement of fibers from both 
cytoplasmic caps. With the formation of fibers comes a break- 
ing down of the nuclear membrane and, in consequence, the 
fibers enter the nuclear cavity and organize the spindle. Some 
of the fibers become attached to the split chromosomes and 
push, draw or pull them to the equatorial plate, halfway between 
the poles. Meanwhile the nucleolus disappears. As _ the 
chromosomes line up at the equatorial plate their daughter halves 
are drawn apart in V-shaped fashion. The split extends and 
eventually one daughter-chromosome is drawn to one pole and 
the remaining half to the other. At the respective poles the 
