CHYTRIDIALES 65 



in the Plasmodiophoraceae. Later workers have, however, 

 generally regarded the organism as a member of this group. 



Our knowledge of the life history of the species is consider- 

 ably confused by contradictions in the accounts of Johnson, 

 Home, Osborn, and Kunkel. According to Johnson the spore 

 germinates by eight zoospores, while Kunkel states that the 

 entire content emerges as a single zoospore. Kunkel says further 

 that the various zoospores which emerge from the spores compos- 

 ing a spore ball may coalesce to form a tiny plasmodium, and 

 that this is capable of infecting the host by passing down into the 

 tuber between its cells. In the host cell the behavior of the 

 protoplast of the parasite seems to be much like that of other 

 species of the family. At maturity several spore balls may exist 

 together in the same cell. Osborn states that immediately 

 preceding spore formation the nuclei fuse in pairs throughout 

 the protoplast, and that this is followed by the reduction divi- 

 sions. Additional investigation of the organism is desirable in 

 the light of the evident contradictions in the published accounts. 



The genus Clathrosorus Ferdinandsen and Winge (1920) was 

 based on the single species,- C. campatiulae Ferd. & Wge. col- 

 lected in Denmark on the roots of Campanula rapunculoides. 

 The organism causes the formation of small galls resembling the 

 legume tubercles. Spore balls somewhat resembling those of 

 Spongospora were found, the individual spores having a minutely 

 warted membrane. The "cruciform" type of nuclear division is 

 pictured. The account is very brief, and knowledge of the life 

 cycle too inadequate to warrant recognition of the genus. The 

 organism is perhaps a relative of Spongospora. 



Excluded Genera 



The following genera, which have been incorporated in the 

 Plasmodiophoraceae in certain recent treatments, are regarded 

 as falling outside the limits of the group as here understood. 



1. Sporom3rxa Leger (1908). 



An organism found in the coelomic cavity of the imago of 

 Scaurus tristis was named Sporomyxa scauri Leger, and made the 

 basis of this genus. Although Leger referred the species to the 

 Plasmodiophoraceae its incorporation in the family does not 

 seem justified. In addition to the fact that it occurs in an 

 animal host, its possession of ellipsoidal spores indicates lack of 



