210 AQUATIC PHYCOMYCETES 



Vegetative part an isodiametric coenocytic or septate tube; 

 generally extending through several host cells 



Vegetative part broadly tubular, nonseptate Rhizosiphon, p. 397 



Vegetative part a narrow septate tube Aphanistis, p. 401 



SUBFAM. PHLYCTIDIOIDEAE 



Sporangium epibiotic or extracellular; resting spore epi- or endo- 

 biotic; vegetative system varied in nature; zoospore cyst usually per- 

 sistent and functional. 



PHLYCTIDIUM (Braun) Rabenhorst 



Flora Europaea algarum, 3: 278. 1868 (sensu recent. Serbinow, Scripta Bot. 

 Horti Univ. Imper. Fetro., 24: 158. 1907) 



(Fig. 19 A-B, p. 318) 



Chytridium, subgen. Phlyctidium Braun, Abhandl. Berlin Akad., 1855: 74. 



1856. Non Phlyctidium Wallroth, Flora cryptogamica Germaniae, 



2:416. 1833. 

 Tylochy triu in Karling, Mycologia, 31: 287. 1939. 

 Hapalopera Fott, Studia Bot. Cechica, 5 (3-4): 170. 1942. 



Thallus epi- and endobiotic, monocentric, eucarpic, the epibiotic 

 part forming the rudiment of the sporangium or resting spore, the 

 endobiotic part producing the unbranched, tubular, peglike, clavate, 

 knoblike, or discoid haustorium; sporangium inoperculate, uni- or 

 multiporous; zoospores formed within the sporangium, posteriorly 

 uniflagellate, generally with a single globule; resting spore thick-walled, 

 borne like the sporangium, asexually formed or sexually after terminal 

 or lateral fusion of two isogamous gametes, one of which has previously 

 come to rest and germinated and the other encysted upon it. 



Primarily parasites and saprophytes of fresh-water algae. 



It is sometimes difficult to determine whether a fungus is a species 

 of Phlyctidium or Rhizophydium. The distinctions given here are no 

 doubt artificial and the genus Phlyctidium has not been recognized by 

 all investigators (Scherffel, 1926a: 186). In practice, however, its sep- 

 aration from Rhizophydium is highly useful. If the haustorium gives 

 definite evidence of being almost isodiametric or is distally expanded, 

 unbranched throughout, and must be depicted as a double rather 

 than a single line, the fungus is placed in Phlyctidium. 



