1908] GATES—REDUCTION IN OENOTHERA 
7 
break apart at the corners where they meet, and before diakinesis is 
reached they are completely rounded off and independent, or they 
frequently remain connected with other mother cells only at the ends. 
In the meantime the cavity of the loculus grows rapidly, so that the 
mother cells, in normal development, usually lie loose in the cavity. 
The events of synapsis and reduction usually go forward simul- 
taneously throughout a flower, with comparatively little variation in 
the different parts of the same loculus or in the different anthers of a 
flower. In one flower, however, wide variation was found in different 
anthers, but comparative constancy in the loculus. One anther of 
this flower was in synapsis, another in diakinesis, another in meta- 
phase of the heterotypic mitosis, and in still another some of the 
mother cells had completed the second mitosis. No abnormalities 
in the cytological condition of this flower were observed. 
SYNAPSIS 
After the stage described in fig. 4, the nucleus increases greatly in 
size, but without an appreciable increase in the size of the cell. The 
single row of sporogenous cells divides, so that there are usually two 
rows of pollen mother cells. Occasionally three or more mother 
cells are found in the cross-section of a loculus. In general there are 
fewer divisions than in the other forms, and this is at least one of the 
reasons why the mother cells are on the average larger than, for 
example, in O. Lamarckiana. 
The resting nucleus of the pollen mother cell increases in size and 
begins to show signs of approaching synapsis. Figs. 12, 13, 14 
show stages in the beginning of this process. A number of these 
Stages were found—although they are uncommon—in the same 
sections with regular synapsis stages. In some cases they occurred 
side by side with mother cells in which the synaptic knot had already 
been formed. A complete series of stages may be found in the same 
section, from the beginning of contraction to the formation of a close 
synaptic ball. The cytoplasm in these cells shows no contraction 
whatever, but is perfectly fixed. For this and other reasons there 
can be no doubt that this is a real contraction stage, leading to synap- 
sis, and not a result of imperfect fixation, as one might judge on first 
examination. 
