Harper. — Cell- Division in Sporangia and Asci. 521 
tion of cellulose, and an analogous conclusion might be drawn 
here as to the relation of the nucleus to the formation of cilia. 
This view would be further strengthened by Strasburger’s 1 
observation on the swarm-spores of Vaucheria , where he 
found the cilia arranged in pairs over the whole surface of the 
spore, and a nucleus just beneath each pair. 
Strasburger believes that in Oedogonium a centrosome lies at 
the base of the mouthpiece as the centre about which the rays 
above mentioned are oriented. The material for the cilia is 
undoubtedly formed in this region at the base of the mouth- 
piece, and if it is also the centre from which materials for 
a new plasma-membrane are diffused outward along the rays 
of the aster which is also formed at this place, we might con- 
sider the process as analogous to that in the ascus. Further 
details of the process in Oedogonium are necessary before the 
value of such a comparison can be tested. 
The total dissimilarity of the process of cleavage in the 
sporangia described and the ascus as I have shown it in the 
above account, makes it necessary to look for the ancestors 
of the Ascomycetes elsewhere than in the lower Fungi. 
Thaxter’s 2 studies of the Laboulbeniaceae have emphasized 
greatly the resemblance of that group to the Florideae and 
the hypothesis of the multiple origin of the Fungi from the 
Algae has gained correspondingly in strength. From this 
standpoint an attempt to homologize the swarm-spore-forma- 
tion in such forms as Oedogonium with the free cell-formation 
in the ascus is not without value. Strasburger has pointed 
out a difference between ordinary cell-division and swarm- 
spore-formation in Cladophora , and it may be that this differ- 
ence has been further developed in higher forms. The 
cleavage in the sporangia of the Phycomycetes described corre- 
sponds to the method of cell division in Cladophora , and it 
may be that the type of division shown in the swarm-spores 
has been developed into that shown in Oedogonium and the 
ascus. It would be especially interesting to know in detail 
1 Schwarmsporen, Gameten u. pflanzliche Spermatozoiden. Hist. Beitr., iii. 
2 Cont. to Mon. of Laboulbeniaceae, p. 251. 
