CANNON: STUDIES IN PLanr Hysrips 171 
before the divisions are completed. It is possible that the same 
plants grown under other conditions might have carried the 
divisions farther. Besides the irregularities in division as just 
given, others, especially in the achromatic figure, were also noted ; 
in some cells the multipolar spindle was seen accompanied by 
many small nuclei. 
Another form of irregularity occurred which is not so clearly 
degenerate but which must also be considered a factor that leads 
to infertility, namely the direct nuclear divisions in cells gathered 
the later portion of the winter. The mother-cells of the nuclei 
which were to undergo direct division were apparently like their 
counterparts in which normal mitosis would occur except as 
regards the structure of the cytoplasm, which retains its primitive 
condition ; that is, a perinuclear zone is not differentiated, and a 
fibrillar layer is not present. The process of amitosis consists of 
a division of the nucleolus, followed by an equal or an unequal 
direct division of the remainder of the nucleus such that a nu- 
cleolus goes to each daughter nucleus. 
The first amitotic nuclear division is usually equal, and the 
result of the division resembles that brought about by the indirect 
method, and also the second division may be equal and thus a 
tetrad group in appearance, much like that normally organized, 
may be formed. Usually, however, the divisions are not equal 
and small nuclei are associated in the same cell-complex with 
larger ones. The extreme is to be seen when the nucleus of the 
mother-cell fragments and the cytoplasm contains numerous small 
nuclei. Some of the forms of direct division are shown by figures 
77, 78 and 79. ee 
Cell-division may or may not follow the direct nuclear divi- 
sions. If it does, tetrads which are like the normal ones except 
as to the presence of small nodes will be formed ; if, however, cell 
division does not take place, monstrous pollen grains result. Since 
the tetrads formed as a result of direct division may be like those 
organized in the regular manner a mere macroscopic examination 
of the mature pollen will give no indication of the genesis of 
such, and hence, it may be supposed, of its ability to germinate. 
By way of general summary, I may say that in the anthers of 
the hybrid cotton one finds both normal and abnormal conditions. 
