130 Mot tier. — Mitosis in the Pollen Mother -cells of 
of radiating loops extending from a central entanglement as is characteristic 
of Liliiim. 
During the complicated rearrangement the cross-segmentation of the 
spireme begins. Portions of the spireme, more especially those appearing 
as loops, may segment into pieces equal to two somatic chromosomes or 
a whole bivalent, but all the pieces or segments which result from the 
transverse separation do not represent whole bivalents. 
The looped portions usually form the rings, U’s, or 8-shaped bivalents, 
while the separated somatic chromosomes make up the X’s and the rods 
lying in contact side by side. In any and all cases where the two members 
or halves of bivalents lie side by side, these forms are due to the approxi- 
mation side by side of the respective halves that were end to end in the 
spireme. 
All chromosomes are formed from the chromatin spireme. Chromo- 
somes do not bud off bodily and full-fledged from the nucleolus. 
The number of bivalents is probably twelve in Acer negundo , and 
thirty-six, or thrice this number, in Staphylea. The larger number of 
chromosomes seems to be correlated with the larger size of the pollen 
mother-cells in these two plants. 
The spindle is developed according to the accepted multipolar type, 
which becomes later bipolar. 
In Staphylea especially, a marked zone of granules (trophoplasmic 
granules) appears about the nucleus during spindle formation and persists 
until the anaphase, when the entire cytoplasm is again more uniform in 
appearance. Collections of oil-drops are very frequently present, lying in the 
plane of the nuclear plate. Later they disappear. 
On their way to the poles the daughter segments are seen to be split 
lengthwise. 
During the construction of the daughter nuclei and later the chromo- 
somes undergo a fragmentation, reticulation, or alveolization into lumps or 
fragments of varying sizes, which are connected with each other by anasto- 
mosing threads. The finely divided state of the chromatin characteristic of 
resting nuclei of similar size was not observed in the daughter nuclei. 
A continuous, smooth and uniform spireme was not observed in the daughter 
nuclei prior to their division. 
The second mitosis presents nothing unusual for Dicotyledonous plants. 
There is no unequal distribution of chromatin to the granddaughter 
nuclei. 
The nucleolus represents material which contributes to the building up 
of the constituents of the cell. It doubtless serves as nutrition for both 
chromatin and cytoplasm, according- to the demand made upon it by the 
activities of the different parts of the living substance. 
