476 BOTANICAL GAZETTE [DECEMBER 
might have acquired secondarily a sexual significance. Thecotheus 
with its ascogonia, and presumably also still earlier oogonia, shows no 
tendency towards this condition. Ihave been unable to find binucleate 
cells either in the paraphyses, in the mycelium, or in any of the vegeta- 
tive cells of this fungus, and am sure that Thecotheus does not possess 
anything comparable to the synkarophyte of the Basidiomycetes. 
The main problem relating to the asci at present is whether they 
are merely eight-spored sporangia or spore mother cells correspond- 
ing to those of the higher plants, and on this point the method of 
spore formation in a polysporous ascus should throw much light. 
As noted previously, I have confined my attention principally to 
Thecotheus on account of the abundance of this apparently very 
favorable form. The possibility that such asci might show transi- 
tional conditions leading over to those found in the sporangia of the 
lower fungi is very suggestive, and, as noted above, BARKER believes 
that in the asci of the nearly related genus Ryparobius he has found 
such transitional forms, although RAmtow believes the ascus of 
Thelebolus shows no such sporangial characters. The distinction 
between typical sporangia and typical asci seems to be sharply drawn. 
In the sporangia of Sporodinia and Pilobolus Harper (99) has 
found that spore formation is by a process of progressive cleavage 
by means of furrows, either from the surface of the protoplasm or 
from vacuoles of the mother cell. The nuclei during the cleavage 
are in a resting stage and are not concerned in the process. Thus 
the formation of an epiplasm is precluded. Harper has described 
the process of cell formation in Synchitrium decipiens, Pilobolus - 
crystalinus, and Sporodinia grandis; while SwINGLE (:03) has 
observed the same process in the sporangia of Rhizopus nigricans and 
Phycomyces nitens. HARPER has pointed out that this process is not 
one of free cell formation in the sense in which the term is used for 
free cell formation in the ascus, in which the cells lie free in the mother 
cell included in the so-called epiplasm. He also concludes that these 
two very divergent methods of cell formation in asci and sporangia 
make it impossible to assume any close relationship between these 
two structures, and this difference is thus made an argument against 
the homology of the sporangium of the Phycomycetes and the ascus of 
the Ascomycetes. 
