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 
Lilium philadelphicum. 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 americannm, 
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 latifolia are typical examples of this condition. But 
very commonly the chromatin contracts awav 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 tigrinum 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. 
