1898 ] CELL DIVISION IN PINE SEEDLINGS 241 
In some of the preparations very definite and distinct radia- 
tions surrounded the nuclei (jig. 2). These radiations are 
rather thick strands of cytoplasm, and do not show the fine 
structure found in spindle threads or in radiations around the 
poles. In the preparations where such radiations were seen 
nearly every cell showed them, whether in the resting condi- 
tion or the early stages of division ; indicating that they were 
produced by the fixing agent. If not caused by this means 
they are probably the result of a streaming of the cytoplasm 
similar to that found in the cells of hairs, on Tradescantia 
stamens. 
Just before cell division commences the nuclei stain very 
readily. The first change to take place in the structure of the 
nucleus is the transformation of the chromatin network into a 
long thread or spirem. When the spirem is almost formed, and 
while the nucleoli are still visible in the nucleus, and before the 
nuclear membrane has disappeared, the spindle begins to form. 
When first seen it consists simply of two rounded or dome- 
shaped prominences (fig. 5), one on each side of the nucleus 
(figs. 6-10). These dome-shaped spindles gradually become 
elongated and pointed until they extend outward to two definite 
points at which centrosomes are often visible (jigs. 10-12). 
These appear as small deeply stained bodies placed just at the 
point of the spindle (figs. 24, 25). In fig. 16 the centrosome 
appears to be lying in a hyaline area which is surrounded by a 
darker portion of protoplasm. At about the time the spindle 
becomes pointed the spirem breaks into a definite number of 
chromosomes and the nuclear membrane disappears. At this 
time the nucleoli are no longer visible, having disappeared in the 
early prophase of division. They are not found again until cell 
division is about complete. The poles are usually approxi- 
mately on opposite sides of the nucleus from the first appear- 
ance of the spindle. In a few cases, however, they were less 
than 180° apart (fig. r2),.and did not become directly opposite 
until quite a late stage of karyokinesis. Radiations are fre- 
quently seen around the poles (figs. 6, 77)- 
