522 Harper . — C ell- Division in Sporangia and Asci. 
how the formation of spermatozoids in Oedogonium compares 
with that of the zoospores. The spermatozoids are known 
to have the structure of the zoopores, but more than one are 
produced in each cell. I have not been able to obtain 
sufficient material for the investigation of this point. Where 
we are to seek the origin of the ascus-type of spore-formation 
remains uncertain except perhaps for the facts in the swarm- 
spore-formation just noted. Brefeld has treated as practically 
one the question as to the presence of sexuality in the 
Ascomycetes and the relationship between the ascus and 
sporangium of the Phycomycetes. It is plain, however, that 
the sexual origin of the ascus-fruit and the relationship of 
ascus and sporangium are entirely distinct problems. The 
ascogonium may be the outgrowth of a fertilized egg and still 
the asci be homologous with the sporangia of Sporodinia , for 
example, where regularly the sexually produced zygospore 
germinates into a branching sporangiophore without the 
intervention of a mycelium. The analogy between such 
a germinating zygospore of Sporodinia and the egg of 
Erysiphe with its ascogonium and asci is quite striking. 
In Sporodinia however sporangia are produced later from 
vegetative mycelia without the preliminary formation of zygo- 
spores. There is thus no obligatory alternation of fruit-forms, 
an indefinite number of sporangial fruitings being followed 
by zygospore-formation. From this type of reproduction, 
which is common among the lower Algae and Fungi, we 
could pass to the condition of things we find in the Ascomy- 
cetes in two ways. First by the suppression of all production 
of sporangia which does not follow immediately on the ger- 
mination of the fertilized egg so that the sexual and asexual 
fruiting bodies should gradually assume the relation of obli- 
gatory alternation ; or it could be assumed that the fertilized 
egg gradually developes an intermediate stage of cell-division 
and growth, by which it produces a large number of asexual 
reproductive bodies before the mycelium which produces the 
non-sexual sporangia or conidia is developed. It is generally 
assumed that the alternation of generations of the Liverworts 
