No. 466] | STUDIES ON PLANT CELL.—VIII. 723 
brane. Or the area may be a cell plate whose halves on division 
finally merge with outer plasma membranes of the cells. The 
spindle fibers which cut out the spore areas in the ascus form 
the basis of a plasma membrane. Thus the fate of all kinoplas- 
mic fibrille seems to be a final return to the undifferentiated, 
finely granular condition so characteristic of plasma membranes 
which according to this theory is the condition from which they 
arose. | 
Thus I believe the liverworts present rather striking evidence 
of a relationship between the centrosphere, polar cap, and the 
free fibrillar condition of spindle formation and establish an 
evolutionary tendency from the first two types of kinoplasmic 
differentiation towards the latter. The free fibrillar type of 
spindle formation is found in a very simple form in this group, 
sometimes with temporary centers, as in the four-rayed figure 
(quadripolar spindle) of prophase, whose poles have accumula- 
tions of kinoplasm in the position of centrospheres. The polar 
caps are likely to prove a much simplified type of centrosphere 
whose kinoplasm is no longer gathered to form conspicuous 
spherical centers. With respect to the problem of the homol- 
ogies and nature of the blepharoplast, the liverworts furnish as 
yet no material assistance and this structure stands at present 
as one of the most interesting puzzles of plant cytology. As 
stated in the beginning, the variety of centrosomes and centro- 
spheres with and without. radiations in various types of the thal- 
_lophytes seems to me too confusing to promise an understanding 
of their relationships at present. 
Grégoire and Berghs (:04) have interpreted the structure of 
the mitotic figure in the germinating spore of Pellia in a very 
different manner from the accounts of Farmer, Chamberlain, 
and myself. They consider the asters to arise through a re- 
arrangement of the cytoplasmic network around the nucleus. 
They affirm that there are no true centrospheres nor any ac- 
cumulations of granular kinoplasm to constitute the centers of 
origin for the spindle fibers or the radiations around the poles of 
the spindle. The centers of the asters (‘‘vésicules polaires”) 
are said to have a vesicular structure and neither they nor the 
nucleus contributes to the building up of the spindle which is 
