Nov. 1913.] Microsporocytes of Oenothera Biennis. 
191 
with the chromatin masses since there is a difference in the way 
the two stain. The protochromosomes are connected by delicate 
strands. 
Figures 4, 5 and 6 show the protochromosomes in various 
stages of transformation, while their chromatin is apparently 
being distributed in the form of granules on the spirem. In 
Fig. 4 there are still six good sized masses although part of the 
chromatin has already been distributed. Fig. 5 shows four large 
masses and two small ones with a spirem forming in the cavity. 
By the time the sporocyte is as far advanced as the one shown in 
Fig. 7 the spirem is complete and the protochromosomes are 
entirely gone. All this time the sporocytes are gradually growing 
larger. 
Somewhat later the chromatin material becomes loosened 
from the nuclear wall and collapses in a mass in the nuclear 
cavity, but the synizetic knot is never so close as in some species. 
Figures 8, 9 and 10 show synizesis in different stages. In figure 
10 most of the spirem can be plainly seen. The granules along 
it are easily made out and the whole spirem is looped and twisted. 
The nucleolus is not confused with chromatin material on account 
of the differentiation of the stain. The nuclear cavity is enlarged 
and frequently the cytoplasm is contracted away from the cell 
wall. The spirem after the synizesis is granular and looped, 
and can be traced for some distance. (Fig. 11.) 
Figure 12 shows a continuous spirem. In the preparation 
the spirem could be traced throughout its complete distance 
without a break. In the drawing the nucleolus seems to cover 
the spirem and obscure its continuity, but in the preparation, 
by focusing, the spirem could be seen to be complete throughout 
its entire length. The spirem is distinctly granular and is thrown 
into loops three of which can not be mistaken and four more can 
be made out without much difficulty. Figure 13 shows loops 
while figures 14 and 16 show seven definite loops. In figure 14 
one loop is filled up with stain. In the next figure (Fig. 15) five 
definite loops show and two masses, one smaller than the other. 
Figure 16 is probably the best figure to show that the spirem is 
continuoiis and is thrown into seven definite loops. Two of 
them have a double twist. The spirem is granular and lies 
between the nucleolus and the nuclear wall. In figure 13, 14 and 15 
the loops are crossed in the center and beneath the nucleolus 
and so the continuity of the spirem can not be observed. The 
looping of the thread shows plainly also in figures 17 and IS, but 
the continuity of the thread can not be seen plainly on account 
of the nucleolus. The spirem is granular. In these two sporo¬ 
cytes (Figs. 17 and 18) the nuclear wall seems to be disappearing 
although in most cases the nuclear wall does not go until the 
chromosomes are formed. 
