eae Pe tire ier ay ante se 
teat 
Pe ee ae 
Ns iy San 
ea oO SRE PEE! SCAG 4 ete i Sea a ap eer av ae eae eee aS 
1900] LHE CELL PLATE IN HIGHER PLANTS 159 
fibers that have been formed after the division was complete, I did 
not determine. If the former supposition is true there would 
seem to be an unusually large number of spindle fibers which 
took no part in the formation of the cell plate. From the fact 
that in all cases observed of the formation of the first cell plate 
no such abundance of regularly arranged fibers was evident, I 
think it probable that these are mostly new fibers. Connecting 
stages, however, may have been overlooked. Their significance 
in either case is not clear. It may be that they build a new 
plasma membrane around each pollen grain inside of the plasma 
membrane of the special mother cell. Further investigation 
upon these late stages of the formation of the pollen grains is 
desirable, 
The process by which the cell plate grows in area is difficult 
te ee with certainty. By comparing stages represented 
in figs. 4-7, 1 have concluded that a part of the growth of 
- cell plate takes place by means of the continued addition to 
tof the substance of the original fibers until they are entirely 
used up. I have already described what seems to be the process 
ihc which the fibers go in the formation of the cell plate. 
eRe the evidence for the complete transformation of at 
ae a of the fibers into the cell plate conclusive. The most 
the 2 € interpretation of fig. 6 seems to me to be that all of 
ing s Soha fibers here shown are the remains of the connect- 
aa Tes shown in fig. g. This interpretation is further 
5). hae by an examination of an intermediate stage ( fig. 
are in oh ngs fibers are not much shorter relatively than they 
while ea 4, but it ws noteworthy that they are further apart, 
facts gah plate is, of course, more conspicuous. These 
coliectin O the conclusion that the substance of the fibers, 
apart, a ie the middle, has simply pushed the fibers further 
While a ee that constitutes the growth of the cell plate. 
tion of the simple mechanical process may account for a por- 
Which seem wth of the cell plate, there are phenomena 
all of the ee indicate that other processes accompany “ in 
€ figures, while there is a large area throughout in 
