306 THE LOWER FUNGI— PHYCOMYCETES • 



and Juel (1902 h; 1921) constitute the literature on the cytology 

 of the forms. Ramsbottom (1915; 1916) has contributed 

 valuable comments on these. In Protomyces the endogenous 

 spores are delimited within the endospore after its extrusion, 

 the chlamydospores are intercalary with a smooth membrane, and 

 the endogenous spores copulate regularly in pairs. 



In the genus Protomycopsis Magnus (1905) the endogenous 

 spores are formed within the extruded endospore as in 

 Protomyces, but they do not copulate. The chlamydospore is, 

 moreover, terminal and provided with a warty exospore. The 

 genus includes at least eight or ten species (Biiren, 1915; 1922), 

 the type being Protomyco'psis leucanthemi Magnus on Chrysanthe- 

 tnum leucanthemum. 



In the genus Taphridium Lagerheim & Juel (Juel, 1902 h) 

 the endogenous spores are delimited in a peripheral layer within 

 the chlamydospore before the extrusion of its endospore. 

 The genus, as known at present, embraces three species, 

 T. umhelliferanun (Rostrup) Lag. & Juel on Umbelliferae, T. 

 rhaetica (Volkart) Maire on Crepis spp., and T. algeriense Juel on 

 Ferula communis. The first named is the type of Taphridium, 

 the second the type of Volkartia Maire (1907:145). Due to 

 ignorance of life cycles and to varying conceptions of generic 

 limits the nomenclatorial situation here has become much 

 confused. In the light of present knowledge the merging of 

 Taphridium and Volkartia seems necessary. In at least one 

 species the spores have been described as fusing in pairs after 

 their escape. 



The position of the family Protomycetaceae in the natural 

 system is in doubt, any disposition of it being to an extent 

 dependent upon the interpretation given to the structures and 

 phenomena just described. Unless the extruded endospore be 

 regarded as a many-spored ascus there would seem to be no reason 

 for incorporating these forms in the Ascomycetes. The earlier 

 view of de Bary that these fungi are intermediate between the 

 chytrids (Chytridiales) and smuts (Ustilaginales) is at least 

 suggestive. Biiren (1915), in his earlier work, regarded the spore 

 mother cells as comparable to asci and termed the whole sac a 

 synascus. He was inclined toward this point of view by his 

 assumption that nuclear fusion occurs in the young chlamydo- 

 spore. His later observations (Biiren, 1922) led him to reverse 

 his opinion, some evidence of nuclear fusion in the copulating 



