1908] GATES—REDUCTION IN OENOTHERA 5 
shows that no line of distinction can be drawn between them and the 
large body readily recognized as the nucleolus. They are then 
smaller nucleoli, not differing essentially in origin from the single 
larger body which is almost constantly present in the mother cell 
during synapsis and prophase, but diverging from the latter some- 
what in their later history. 
In the earliest stages studied, the young meristematic cells of the 
anther primordia are very small (figs. 1, 2), and the tissues are wholly 
undifferentiated, except the epidermal layer. Usually several smaller 
nucleoli are present in each nucleus of the meristematic cells, in addi- 
tion to the larger nucleolus. Compared with the cells of the anther 
wall when they are no longer meristematic, the smaller nucleoli of 
the former are about the size of the nucleoli of the latter, which are 
approximately equal in size. There is nothing in the latter corre- 
sponding to the larger nucleolus of the meristematic cells. Probably 
afterward one of these nucleoli enlarges as the cell increases in size, 
or it is possible that the nuclei of meristematic cells are always derived 
from previous ones which already possess a large nucleolus. 
Chromatic staining bodies are also found closely appressed to the 
nuclear membrane in all the meristematic cells (jigs. 1, 2). This 
tendency for chromatic material to accumulate on the nuclear walls 
gives these nuclei a characteristic appearance. ‘These bodies often 
appear like a thickening of the membrane itself. 
At the next stage studied many cell divisions have taken place, 
and the sporogenous, tapetal, and wall tissues have been differentiated. 
The sporogenous cells have increased enormously in size, and form 
a single row in longitudinal section down the center of the anther, the 
walls of these cells being especially thickened and distinct (fig. 3). 
The cells of the surrounding tapetal layer have also increased greatly 
in size and are distinctly marked off from the sporogenous row. In 
the Sporogenous cells the nuclei (fig. 4), though much increased in 
size, have not increased in proportion to the cytoplasm. The large 
nucleolus, much larger than in the earlier stage, is now a conspicuous 
object in the nucleus. Smaller nucleolar bodies are almost invariably 
Present, but masses are no longer found attached to the nuclear 
membrane. (The characteristic masses, however, may remain for 
some time attached to the nuclear walls of the tapetal cells). 
