46 BOTANICAL GAZETTE [JULY 
elaters of liverworts, which are, historically, sporogenous cells 
and often develop like sporogenous cells, even up to the spore 
mother-cell stage. In the formation of the ascospore, the function 
of the centrosome is not the same as during the mitotic divisions 
in the ascus. Other examples might be cited. 
That the function of the blepharoplast is somewhat peculiar 
must be admitted. Radiations, however, and spindle fibers, 
which are often the most conspicuous accompaniments of cen- 
trosomes and centrospheres, are actively concerned in movement 
and are not essentially different from the radiations or cilia of 
blepharoplasts. In form and function centrosomes present so 
much diversity among themselves that the peculiarities of the 
blepharoplast need occasion no surprise. One has only to com- 
pare the typical spherical centrosome with the rod-like centro- 
some of Dictyota, the hollow cylindrical spindle of some diatoms, 
and with the centrosome which forms the Hauéschicht of the 
ascospore. 
We should conclude, therefore, that centrosomes, centro- 
spheres, and blepharoplasts are historically related, and with 
their radiations, spindle fibers, and cilia are only different mani- 
festations of kinoplasmic activity, movement in all cases being 
the principal function. 
Pellia, with the prominent aster and centrosphere of its ger- 
minating spore becoming less and less distinct in succeeding 
mitoses until a condition is reached resembling that which pre- 
vails in the flowering plants, presents in its own life-history 4 
great reduction of the aster and the disappearance of the cen- 
trosphere. 
I am deeply indebted to Professor Strasburger for his kindly 
courtesy and helpful suggestions during my work in his labora- 
tory. 
SUMMARY. 
. The principal part of the work deals with the first three 
seein in the germinating spore of Pellia epiphylla. We have 
not intended to attack the excellent work of previous investi- 
gators, but rather have attempted to extend a little farther a 
knowledge of the phenomena of mitosis. 
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