Division in the Root of Vicia Faba. 17 
7 
to be due to the chromatin. When the thread first forms, it 
is of a bluish crimson tint and is formed from the nuclear sub- 
stance. This nuclear substance contains but a very small 
quantity of chromatin, so that while the nuclear thread con- 
tains some chromatin derived from the nuclear material, the 
quantity thus obtained must be relatively small. The chro- 
matin which eventually fills the thread and gives it its dense 
bluish black color is mainly nucleolar material. We have 
here merely a temporary change in form. The nucleolus is 
chromatin material, and the chromosomes are chromatin 
material. In the resting stage we find the chromatin chiefly 
massed together in this large bluish black nucleolus; in 
the dividing nucleus, the nucleolus is transferred from its 
aggregated condition and is distributed along the nuclear 
thread. Therefore, as the reserve chromatin mass, 7. ¢., the 
nucleolar substance is passing out into the nuclear thread, 
the nucleolus itself gradually disappears. 
We can now proceed from the stage where the spirem has 
split transversely into the chromosomes. The nuclear mem- 
brane has already disappeared, it having started to disappear 
as the nucleolus passes its substance to the spirem. The 
chromosomes split longitudinally, and thus are formed the 
daughter chromosomes (Fig. 15). There are in most cases 
five daughter chromosomes. Four is not an unusual num- 
ber to find, but five seems to be the more common. The 
daughter chromosomes now pass to opposite ends of the cen- 
tral spindle. They collect at the ends of the spindle and for 
a time retain their individuality (Fig. 16). Soon the individual 
chromosomes can no longer be distinguished, since they 
aggregate to forma small dense blue-black coil (Figs. 16 and 
17). 
Reappearance of the Nucleolus—The chromosome coil 
now begins to heap up its chromatin material and we have the 
beginning of the formation of the nucleolus. The very earliest 
I2 
