6 BOTANICAL GAZETTE [JULY 
Figs. 5-10 are from drawings of other nuclei at this stage of develop- 
ment. In the majority of cases one or two smaller nucleoli occur 
in addition to a single large one, but rarely (fig. 6) two large nucleoli 
of equal size may be found; and very frequently the number of small 
bodies, of equal or unequal size, may be greater, reaching as many as 
five or six. Figs. 5, 7, 8, 9 show these in various stages of fusion with 
each other and with the large nucleolus.: They are thus not in any 
sense autonomous bodies. It appears that usually these fusions 
take place until only one large nucleolus and one or two smaller ones 
are present during synapsis and diakinesis. But occasionally the 
fusions do not take place, and several of these bodies may then be 
present in the later stages. The number of these nucleoli finally 
present depends, then, largely upon the amount of fusion which has 
previously taken place between them. In the later stages one large 
nucleolus is almost invariably present and usually a smaller one 
bearing a certain proportion to the larger in size, though the latter 
may vary in size and number as already stated. There is usually 
a clear area around the large nucleolus, as in the earlier stage, and 
threads of the reticulum may or may not cross this and appear to be 
attached to the nucleolus (fig. 4). The reticulum of the cytoplasm 
usually stains rather more deeply at this time than that of the nucleus. 
It may as well be stated at this time that in the resting nuclei of the 
pollen tetrad and in.the nuclei of the nearly mature pollen grains of 
Oenothera one finds (fig. rr) the same condition of the nucleoli as 
in the mother cells, namely, usually one large and one small nucleolus 
bearing a rather definite size relation to each other, with sometimes 
additional small ones. 
The sporogenous rows are differentiated from the tapetum by 
the greater growth of the cells, nuclei, and nucleoli of the former. 
At the same time they are distinctly marked off by the formation of a 
continuous thickened wall between tapetum and archesporium 
(fg. 3). It.is obvious that as the cells and nuclei increase in size, 
the nucleolus grows also. Up to the time of synapsis the mother cells 
usually form a compact tissue, but about this time the cells begin to 
iss NICHOLS (21) figures what are in all probability stages of fusion of la 
and small nucleoli in Sarracenia pollen mother cells, but interprets them as a buddi 
off of small bodies from the nucleolus. e budlike attachments to the nucleolus 
frequently observed by other authors are doubtless to be explained in like manner. 
