304 BOTANICAL GAZETTE [OCTOBER 
but simulates the outline of the cell and its chromatic material is 
distributed unevenly throughout the nuclear cavity. Several 
large masses of chromatin are mingled with chromatic threads 
which extend out from them in various directions (figs. 28, 29). 
The loculi containing these tetrads also contain densely stain- 
ing tapetal cells. These cells still have large vacuoles, but the 
cytoplasm stains more densely than in earlier stages and their 
nuclei contain one nucleolus each. Outside the tapetum is the 
flattened layer of cells, and beyond this the remainder of the wall 
is still undifferentiated. 
Later, when the microspores have broken away from the old 
mother wall, the endothecium with its spirally thickened cell walls 
forms just beyond the flattened layer. The tapetal cells, in general, 
-are still in good condition, some of them centrally located having 
increased very greatly in size and number of nuclei. Compare 
the tapetal cell (fig. 33) which was magnified 810 times with the 
microspore (fig. 30) which was taken from a loculus of the same 
age and magnified 1620 times. The number of nuclei in these 
tapetal cells may reach as high as 11 or more. These unusually 
large cells show stages in disintegration, and it is difficult to find 
one which has not begun to break down. A large number of nuclei, 
ranging from 6-13 in the tapetal cells of Hepatica acutiloba, has 
been reported by CouLTrer (14). SCHAFFNER (39) in his descrip- 
tion of Typha latifolia states that the tapetal cells increase greatly 
in size while the tetrads are forming, but speaks of but 2 nuclei 
being formed in each cell. 
When the microspores escape from the tetrad the chromatin 
of their nuclei consists of heavy, anastomosing strands which soon 
give rise to several distinct masses of chromatin connected with 
each other by more or less delicate threads. In by far the greater 
number of cases, if not always, these masses correspond in number 
with the haploid number of chromosomes (fig. 30). No nucleolus 
is visible at this time. There is evidently no true spirem formed 
in the division of the nucleus to form the generative and tube cells, 
but the rather imperfect reticulum of the very young microspores 
gives rise directly to the chromosomes at a considerable time before 
the organization of the spindle. It is a very common occurrence 
