FAULL: DEVELOPMENT OF ASCUS. 
101 
developed from a cell removed but one from an ascus and this cell 
may contain a single nucleus (pi. 11, lig. 66). 
General Considerations. 
The problem of the origin of the Ascomycetes must be attacked 
along two main lines, namely, a determination of the homologies of 
the ascus, and an appreciation of the phenomena associated with the 
sexuality of the group. These, it is to be pointed out, are separate 
questions, although it is also true that a final solution can be effected 
only after a consideration of both. The present research has only 
to do with the question of the homologies of the ascus. 
Asci are now generally regarded as asexually produced spore 
sacs on hyphae which are outgrowths of a fertilized organ. Most 
botanists agree on the view that the Ascomycetes have not lost the 
sexual method of reproduction, and that in some of them at least 
there are functional sexual organs. What was a conviction of De 
Bary’s has been proved by the researches of Harper (: 00) and 
Thaxter (’96) to be a reality. The sexual organs are borne on a 
mycelium that follows the germination of the ascospores, and from 
the fertilized oogonia or ascogonia there grow out the ascogenous- 
hyphae, and it is from the cells of the latter that the asci arise. 
These observations may, I think, be assumed without further 
remark to be correct. The next question that arises, and on which 
there is not such unanimity, is in regard to the ancestrak homologue 
of the ascus. 
On this subject four suggestions have been offered: (1) that the 
ascus is a descendant of the sporangium of the higher Mucorineae 
through the Hemiasci, a theory that was propounded and stoutly 
maintained by Brefeld ; (2) that the ascus is a derivative of the 
sporangium (or zoosporangium) of the Oomycetes; (3) that it is a 
new feature without a homologue outside the Ascomycetes; and (4) 
that it is a modification of the carpospore of the Florideae. 
The phenomena of the early stages in the development of the 
asci unfortunately do not throw much light on this matter, unless, 
indeed, to confirm the view that they are coenogenetic organs. 
The fusion of nuclei within the young asci, the phenomenon to 
which I especially refer, is a puzzling feature, one that is as yet 
