370 Gates and Rees . — A Cytological Study of 
Even thought possibly a certain amount of derangement of the nuclear 
content takes place during fixation, yet it is clear that these nuclei represent 
a peculiar physiological condition of the nucleus at the onset of synizesis. 
This is indicated by the manner of their occurrence, for usually the cells of 
a loculus will all show approximately the same condition, while adjacent 
loculi in the same section will be in other stages of development. Thus 
Figs. 8 and 9 are from one loculus, and Figs. 7 an d 10 f rom an adja- 
cent one. Typical synizesis, and later postsynaptic spireme stages (Figs. 
11-12), may also occur in the same slide or in different flowers of the 
same section. Since synizesis itself and the later spireme stages are 
universally recognized as normal developmental stages, the same status must 
be accorded to the transition stages represented by Figs. 7-10. 
All the above stages are exact duplicates of conditions described by one 
of us in Oenothera rubrinervis (Gates, 1908 , see PL I, Figs. 12-15), and in 
Oe. gigas (Gates, 1911 , see PI. LXVII, Figs. 2-6). Fraser ( 1914 ) has also 
figured in Vicia Faba (Figs. 2, 3) conditions very similar to our Figs. 6-10. 
In Oenothera there was evidence of expansion or growth of the nuclear 
membrane at this time, as well as contraction of the nuclear contents. 
Lawson’s ( 1911 ) view that in synizesis there is ‘a great accumula- 
tion of sap within the nuclear cavity ’ which ‘ causes great osmotic pres- 
sure ’, producing a distension of the nuclear membrane, is quite inade- 
quate to explain the phenomena observed. His results with Smilacina 
as to the absence of. any contraction of the nuclear content at this period 
have not been confirmed in any other plant, and McAllister ( 1913 ) has 
since figured typical synizesis in this genus. Consideration of all the 
results show that while there is a certain amount of expansion or growth 
of the nuclear membrane both in Oenothera , Smilacina , and Lactuca , 
there is also a notable contraction of the nuclear reticulum at the same 
time. In Lactuca and also in Oenothera there is clear evidence of a 
delicate membrane surrounding the reticulum in the early stages of its 
contraction. 
In Lactuca the evidence for contraction of the nuclear reticulum is 
conclusive, but there is also clear evidence of growth of the nucleus during 
the later stages of synizesis (Fig. 4). This growth and a number of other 
size relationships are shown in the table of comparative measurements 
given below. 
Each figure given is the average of twenty-five measurements, or 
in a few cases ten measurements. The range of variation was small except 
in the synizesis stage of the cells in L . Scariola marked (*). The number 
of measurements, while not large, was found to be sufficient for the present 
purpose. Reading down the vertical columns, there is seen to be a steady 
growth in the size of the mother-cell from the presynaptic to the postsyni- 
zesis stage. The same is true of the nucleus during this period. The 
