1909] SCHAFFNER— REDUCTION DIVISION IN AGAVE 201 



myxomy 



the plasmodium. 



if synizesis. — As soon as the extended and delicate 



mos 



ly appear in synizesis. There are 

 all types of contraction. The chromatin may stretch across the center 

 of the nuclear cavity (figs. 6, 8) ; it may be contracted at one side with 

 the nucleolus (fig. 7) ; or it may be balled up at one side of the cavity 

 with the nucleolus lying free (fig. 10). In some cases the mass is in 

 the center, and often the nuclear membrane is injured by the irregular 

 expansion of the nuclear cavity (fig. 9). The period of development 

 during which synizesis occurs is comparatively long, the anther 

 lengthening greatly in the meantime. The anthers of Agave thus 

 make a most favorable object on which to determine definitely the 

 tage when contraction must be looked for in the living material. A 

 thorough study was therefore made of unstained as well as of stained 



familiar 



of the cells in unfixed anthers. 



Study of living cells.— Having ascertained the stage when synizesis 

 occurs in killed material, a study was made of living anthers during 

 the last two weeks in June, 1908, at Columbus. The anthers were 

 examined immediately after removal from the plant. In some cases 

 cross-sections were cut, in others the stamens were cut into short 

 pieces and the sporocyte tissue squeezed out and mounted in water. 

 fi oth methods were satisfactory. In none of the numerous anthers 

 studied during the two weeks was there the slightest evidence of 



syndesis. In the great majority of cases the nucleolus is in the center 

 °f the nuclear cavity; occasionally it is somewhat to one side; and 

 v ery rarely near the nuclear wall, as is almost universal in the synizesis 

 of the killed material. The nuclei look large, clear, and vesicular, 

 * lth granules and flaky material (no doubt the chromatin) scattered 

 throughout the cavity. The synizetic knot would certainly be visible 

 *ere one present. In the killed material the synizetic mass shows 

 nearly as distinctly in unstained as in stained material. The same 

 ^disturbed condition was found in all the cells in every possible 

 s a ge in the period before rV,™™^™ fnrmntion. The fact that the 



cav 



form 



■ / -^*^ A ^W*" A AAA |-^ X^i^A V -* ^— * A A AA ^* ^**g*^ ^ — — 



lty ' while ^ synizesis they are usually near or against the nuclear 



