1918] OTTLEY—IMPATIENS 303 
draws away from the cell membrane at various points. At this 
stage cellulose begins to be deposited about the cell and when 
the chromosomes have reached the equatorial plate a broad cell 
wall of cellulose is formed (fig. 27). As the chromosomes shorten 
and thicken, they become smooth in outline-and numerous fibers 
heavier and longer than those mentioned for an earlier stage (fig. 23) 
appear within the nuclear cavity. These fibers seem to have no 
apparent relation to the fibers of the kinoplasmic region, although 
at this time the nuclear membrane has become indistinguishable 
from the cytoplasm at various places (figs. 24, 25). The fibers are 
tufted and may extend from a given chromosome across the nuclear 
cavity to other chromosomes or to the nuclear membrane. At 
this time no nucleoli are visible within the nuclei and there is the 
possibility that their substance has assisted in the formation of the 
ers. 
After the nuclear membrane has entirely disappeared many 
fibers appear about the chromosomes (fig. 26). They extend 
beyond what was the original area of the nucleus and doubtless 
there has been a union of intra- and extra-nuclear fibers in the 
formation of the multipolar spindle (fig. 26). By the time meta- 
phase is reached the spindle has become sharply bipolar and 
extends across the entire cell (fig. 27). The cytoplasm surround- 
ing the spindle has lost the dense granular appearance of the early 
prophase stages and stains less densely than does the peripheral 
region. 
While I am not willing to make an unqualified statement 
regarding the number of bivalent chromosomes, it seems most 
probable from the study of the heterotypic divisions in the mega- 
spore and microspore mother cells that the haploid number is 7, 
as I have been unable to count more than that number. No 
stages in microsporogenesis were obtained between metaphase 
of the heterotypic division and the tetrads following the homotypic 
ivision. 
When the tetrads are formed the microspores are surrounded 
by the very thick cellulose wall of the mother cell. Each micro- 
spore is a little over 3 times longer than wide and possesses a 
reticulated membrane. At this time its nucleus is not spherical, 
