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 dehcate 

 strands. 



Figiires 4, 5 and 6 show the protochromosomes in various 

 stages of transfoniiation, while their chromatin is apparently 

 being distributed in the fonn 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 fonning 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 dra-wing 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 distincth' granular and is thrown 

 into loops three of which can not be mistaken and four more can 

 be made out without much difficult^^ 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 

 continuous 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 plainl}^ also in figures 17 and 18, 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 IS) the nuclear wall seems to be disappearing 

 although in most cases the nuclear wall does not go until the 

 chromosomes are formed. 



