1915] YASUI—DIOSPYROS KAKI 367 
Microspore formation 
There is no marked difference between the primary sporogenous 
cells and the primary wall cells before the latter begin to divide. 
Two periclinal divisions give rise to three outer wall layers and a 
tapetal layer. Two or three successive divisions separate the 
primary sporogenous cells from the mother cells. At the same 
time the uninucleate tapetal cells become very distinct between the 
sporogenous tissue and the wall layers, the latter of which become 
more and more flattened. 
During the comparatively long resting period, the spore mother 
cell increases in size, its protoplasm becomes denser (but not so 
dense as that of the tapetal cells), and the nucleus becomes large 
(pl. fig. 1). The nucleus contains rather a small amount of 
chromatin granules associated with the fine linin network, 
and also a remarkably large nucleolus and several small ones 
(pl. figs. 2, 3). 
In some cases I observed the larger chromatin granules appear- 
ing in pairs, but this did not seem to be the usual situation. e 
reticulum is denser at the outer part of the nuclear cavity than 
within. During presynapsis certain connections between the 
chromatin granules disappear, so that the reticulum gradually 
becomes simpler in structure. At the maximum of synapsis the 
chromatin substance appears like a mass of granules (pl. figs. 4 
and 5). 
There is no morphological connection between the chromatin 
reticulum and the nucleolus, although they seem to occur in very 
intimate relationship. A great many nucleolus-like bodies were 
observed close to the chromatin thread, near the large nucleus, but 
in other cases there was no such relationship (pl. fig. 4). In the 
presynapsis stage the double nature of the chromatin thread is not 
clear, but it becomes gradually evident with the loosening of the 
thread (pl. figs. 6, 7). 
Before 1895, when Moore called attention to the synapsis 
stage as an important period in the history of the nucleus, this stage 
was ignored. Since that time it has attracted chief attention, 
and is regarded in general as an important event in the history 
