290 BOTANICAL GAZETTE [APRIL 
generally admitted. Some writers, however, still regard it as due 
-to imperfect fixation.’ This stage was first called “synapsis” by 
Moore in 1895; and many cytologists have come to regard it as 
an important and critical stage, when the actual fusion of the 
maternal and paternal chromosomes occurs. 
Lawson presents a different explanation of the condition 
observed. He interprets the phenomenon as simply a growth 
period of the nucleus, during which the increased osmotic pressure 
within the nucleus causes the absorption of a considerable amount 
_of cell-sap, and the consequent increase in size of the nucleus. In 
this enlargement the chromatin mass is left behind. The char- 
acteristic position of the chromatin mass at one side of the nucleus, 
according to Lawson, is due to the fact that the extension of the 
nuclear cavity always takes place in one direction, that is, on the 
side toward an intercellular space where there is least resistance 
from the neighboring cells. 
Since the publication of Lawson’s paper, the writer has studied 
the synaptic stages in the buckwheat with special reference to the 
comparative size of the nucleus and chromatin mass before and 
during synapsis. There is certainly an increase in the size of the 
nucleus during the synaptic stages, as will appear from a compari- 
son of figs. 3, 4,and 5. It seems equally certain that the chromatin 
mass occupies a much smaller space during the ‘“‘balled-up” con- 
dition than it does either before or after this stage. The stage is 
evidently of considerable duration, longer than all the later stages 
in the heterotypic division combined. 
It is of course possible that the contraction is due to imperfect 
fixation, that the nuclear matter is for some time in such-a condition 
that it is impossible to preserve its structure by any known method. 
A contraction at this stage, however, is of constant occurrence, and 
the chromatic material has a characteristic appearance after the 
‘contraction’? which differs markedly from its appearance before. 
The same conditions were found in Houstonia; and in the following 
descriptions it will be assumed that synapsis is a normal stage. 
A comparison of the nuclei before and after synapsis is rendered 
t A full discussion of this subject, together with citations of literature, is given by 
Grécorre (17, pp. 332-335): 
