CHYTRIDIALES 



79 



Fig. 15. — Pleolpidium 

 monohlepharidis (Cornu) 

 Fischer in fusiform en- 

 largements of hyphae of 



of the parasite being so tightly appressed to that of the host 

 that no line of separation between the two is visible. Conse- 

 quently, a parasitized host sporangium may be easily mistaken 

 for a normal one. The species occurring in 

 the hyphae of the host stimulate the for- 

 mation of pronounced fusiform or ellipsoi- 

 dal enlargements, and the thallus at matur- 

 ity completely fills the lumen of the hypha 

 at the point of its enlargement. The thal- 

 lus then functions as a swarmsporangium. 

 It is thin-walled, smooth and hyaline, and 

 forms one or more inconspicuous, short exit 

 tubes indefinite in position. Other thalU 

 develop into resting spores. These lie free 

 in the host cell as brownish spheres, and 

 have a thick, finely echinulate wall. In its 

 relation to the host cell the thallus resem- ,, , . , ^ t,, , 



Monoblephans. (a) inal- 



bles that of Rozella of the Woronmaceae lus of parasite. (6) Rest- 

 but in that genus fragmentation of the ing spore of parasite. 



, . 1 p . • (After Cornu 1872.) 



thallus at maturity results m the formation 



of a sorus of sporangia, while the swarmspores are biciliate. The 



following species are the best known. 



P. araiosporae (Cornu) v. Minden — 'in sporangia of Araiospora. 



P. apodyae (Cornu) Fischer — -in sporangia of Apodachlya. 



P. blastocladiae v. Minden— in sporangia of Blastocladia. 



P. monoblepharidis (Cornu) Fischer (Fig. 15)— in hyphae of Monoblepharis. 



P. cuculus Butler — -in sporangia of Pijthium. 



8. Plasmophagus De Wildeman, {Ann. Soc. Beige Micros., 

 19:219, 1895). 

 A single species, P. oedogoniorum DeWild., in the vegetative 

 cells of Oedogonium, comprises this genus. Resting spores have 

 not been observed. The thallus tends to fill the host cell as in 

 the preceding genus, but the two walls remain distinct. The 

 thallus enlarges as the host thread develops, and failure of the 

 latter to form the usual cross walls may result in a long cell fiUed 

 by the parasite. Sometimes several thalH occur in the same host 

 cell. The thallus at maturity functions as a sporangium, and 

 uniciliate swarmspores escape through a short inconspicuous 

 papilla. The sporangial wall is assumed relatively late, the 

 naked protoplast, in early stages, being indistinguishable from 

 that of the host. 



