Jan., 1907.] Synapsis and Synizesis. 45 



cytoplasm is often expanded to a considerable extent by the 

 killing fluids in common use. Figure 2 represents such a case. 

 It represents the upper nucleus of a two-celled embryosac of 

 Li Hum philadelphicmn . The killing fluid was the stronger 

 chrom-acetic acid solution. The nucleus is in the resting 

 stage and is not contracted as appears from a comparison 

 with the lower nucleus of the same sac, where the cytoplasm 

 is in the normal condition in contact with the nucleus. 

 When the nuclear membrane has disappeared in the pro- 

 phase of the reduction division the wall of the large vesicular 

 nuclear cavity presents a favorable object for such expansions. 



Recently Cardiff* has put forward the tentative opinion 

 that the one-sided position of the chromatin mass is due to grav- 

 ity. That this is not the case can easily be discovered by a study 

 of cells whose position is known during life and during the killing 

 process. Figures 3 and 4 are sections of microsporocyte tissue 

 from the microsporangia of Marsilea quadrifolia sectioned in the 

 original vertical position. The synizesis has been perfectly sym- 

 metrical. The chromatin knots all being toward the periphery, 

 up and down and to both sides in central sections. Evidently 

 gravity had nothing to do with the phenomenon, at least from 

 a physical point of view. The action was apparently the same 

 as in the case of the onion roots. The hard wall of the sporocarp 

 was probably an important factor in producing the condition. 



Some have supposed that the contraction is always around 

 or in contact with the nucleolus. This is far from being the 

 case. In the various plants investigated by myself one might, 

 in individual preparations, even come to the opposite conclusion. 

 The facts are that the chromatin may be massed around the nu- 

 cleolus and have a central position in the nucleus as in Figure 9, 

 which represents a microsporocyte of Erythronium americanum, 

 or it may have a lateral position, in some cases merely touching 

 the wall of the nuclear cavity, in others crowded closely against 

 it. The nucleolus may appear on one side of the chromatin knot 

 either connected with it or very loosely attached and appearing 

 as if violently squeezed out of the chromatin mass during its 

 contraction. Figures 7 and 8 representing microsporocytes of 

 Sagittaria latijolia are typical examples of this condition. But 

 very commonly the chromatin contracts away from the nucleoli, 

 which then lie free in the nuclear cavity, or are crowded against 

 the wall of the cavity and represent the "sickle stage ". Figures 

 10 and 11 are microsporocytes of Lilium tigrinmn which show 

 these conditions. The synizetic knot is sometimes on the side 

 of the nucleus lying against the greater mass of cytoplasm (Fig. 7) 



♦Cardiff, Ira D. A Study of Synapsis and Reduction. Bull. 

 Torr. Bot. Club 33 : 271-306. 1906. 



