324 AQUATIC PHYCOMYCETES 



KEY TO THE SPECIES OF PHLYCTOCHYTRIUM 1 



Sporangium wall smooth, not ornamented 



Sporangium with a single apical or lateral discharge papilla 



Sporangium spherical, subspherical, ovoid, ellipsoidal, pyriform 

 or domelike, sessile, apophysis with or without rhizoids 

 Sporangium predominantly short-ovoid or pyriform, with an 

 apical discharge pore; not proliferating; apophysis spheri- 

 cal, apparently without rhizoids P. hydrodictyi, 2 p. 326 



Sporangium predominantly ovoid, with its long axis parallel to 

 that of host cell; with a single large lateral discharge pore; 

 internally proliferating; apophysis spherical bearing deli- 

 cate rhizoids P. proliferum, p. 327 



Sporangium predominantly narrowly ellipsoidal; on marine 



algae P. japonicum, p. 327 



Sporangium predominantly spherical, subspherical, domelike, 

 somewhat pyriform or ovoid, with a blunt rounded apex, 

 apophysis always bearing rhizoids 

 Sporangium spherical or pyriform 



Sporangium spherical; resting spore, where known, with 

 bluntly spiny wall 

 Sporangium 5-7 \x in diameter, with an apophysis of the 



same size; rhizoids limited, delicate. ... P. equale, p. 328 

 Sporangium 10-40 u, in diameter; apophysis much small- 

 er than the sporangium; rhizoids extensive 

 Sporangium with a cylindrical discharge tube 18-20 {i 



long P. longicollum, p. 328 



Sporangium with a sessile discharge pore . . .P. hallii, p. 329 

 Sporangium spherical or broadly pyriform; resting-spore 



wall warty P. closterii, p. 33 1 



Sporangium subspherical, ovoid, or domelike, apophysis ex- 

 panded laterally, or subspherical 

 Rhizoids arising from a single main axis laterally placed on 



apophysis P. laterdle, p. 332 



Rhizoids arising from a basal main axis on apophysis, or 

 from several axes 

 Apophysis minute; on Chlamydomonas ... P. vernale, p. 332 

 Apophysis conspicuous; on other algae . . P. lagenaria, p. 332 

 Sporangium narrowly obpyriform, rarely ellipsoidal, sessile or on 



a slender stalk P. chaetophorae, p. 333 



1 See also P. punctatum and P. irregulare Koch (1957), and recently described 

 taxa, p. 346. Note that key is not strictly dichotomous. 



2 Further observations will probably show that rhizoids are formed. 



