1900 | CURRENT LITERATURE 149 
outcome of his studies upon the ascus, and the conclusions are of great inter- 
est in relation to the problem of the origin of that organ and the group of 
fungi characterized by its presence. Harper studied the sporangium of Syn- 
chitrium, Pilobolus, and Sporodinia, and found the method of cell-division 
essentially similar in all forms. 
The protoplasm of the sporangium becomes divided by “cleavage fur- 
rows” that start from the plasma membrane (Hazéschicht) or from vacuoles. 
The cleavage is progressive and gradual, and in large sporangia very irreg- 
ular, separating masses of multinucleate protoplasm of varying sizes. The 
cleavage furrows divide the protoplasm in a manner aptly termed “cleav- 
age by constriction,’ and should be carefully distinguished from free cell 
formation. In cleavage by constriction there can be no epiplasm, and the 
process is initiated from the plasma membranes, either on the outside of the 
sporangium or around the vacuoles. This fact indicates that these two forms 
of plasma membranes are more closely related than may be generally 
believed. 
True free cell formation is illustrated by the development of spores in the 
ascus. Here areas of protoplasm around the nuclei are cut out from the 
general mass of cytoplasm by the activity of the fibrilla of an aster, and such 
fibrilla are of course identical with the fibers that make up the spindle of a 
nuclear figure. These fibrilla bend down and around the nucleus from the 
center of the aster and cut out a region of cytoplasm, which later becomes 
more definitely bounded by the spore wall. After spore formation there is 
left in the ascus a quantity of epiplasm, which, having no nuclei, must finally 
become disorganized. 
The importance of these investigations to the problems of the relationships 
of ascus and sporangium cannot be stated too strongly. To one who believes 
firmly in the great value of comparative cytological studies as a test of rela- 
tionship between groups of plants, the evidence seems overwhelming against 
the views advanced by Brefeld. It would be almost inconceivable that two 
homologous organs, such as some suppose the sporangium and ascus to be, 
could present protoplasmic activities of such diverse characters. The entire 
trend of cytological phenomena is against such a hypothesis. These investi- 
gations furnish perhaps the most striking instance of the value of cytological 
work as an aid and safeguard in speculation upon problems of plant phy- 
logeny. 
The paper also discusses several other topics of interest and value, but 
4 most important conclusions are perhaps those outlined above.—B. M. 
AVIS, 
