436 AQUATIC PHYCOMYCETES 



Thallus monocentric, eucarpic, ordinarily polyphagous, consisting of 

 a reproductive rudiment (usually the body of the encysted zoospore) 

 and several branched or unbranched rhizoidal axes only the ultimate 

 tips of which are endobiotic; sporangium inoperculate, with one or more 

 discharge papillae; zoospores formed within the sporangium, pos- 

 teriorly uniflagellate, usually with a single globule, generally discharged 

 in a compact group imbedded in a gelatinous matrix from which they 

 eventually escape; resting spore thick-walled, borne like the sporangium 

 on the thallus, upon germination functioning as a prosporangium. 



On algae, insect integuments, and debris; abundant in soil. 



As originally described in Fischer's monograph on the Phycomycetes 

 the genus Rhizophlyctis also included Rhizidium Braun. Schroeter (1893 : 

 79) reestablished Rhizidium in its original sense and limited it to 

 Rhizidium mycophilum Braun. Rhizophlyctis was retained as a genus but 

 was not clearly separated from Rhizidium by him. This was later done 

 by Minden, who emphasized the presence of a single main axis in the 

 rhizoidal system of Rhizidium as contrasted with several axes, often of 

 the same degree of development, in Rhizophlyctis. This morphological 

 distinction is maintained here. Occasionally, as in Rhizophlyctis bor- 

 ncensis, the rhizoidal system may rise from a single central axis, but 

 this is never broad and taproot-like, as in Rhizidium. The other extreme 

 in rhizoidal development is to be found in Rhizophlyctis petersenii, 

 where a number of broad rhizoids emerge from the rudiment of the 

 sporangium (Fig. 28 A, p. 440). Further investigations may show these 

 differences to be of no great significance, and the genus then should be 

 merged with the older Rhizidium. 



Johanson (1944) segregated the well-known Rhizophlyctis rosea de 

 Bary and Woronin from Rhizophlyctis and placed it in a newly erected 

 genus Karlingia. She based her decision on the presence of an endooper- 

 culum (see p. 437). There is little doubt from both the description and 

 figures that de Bary and Woronin's fungus possessed such a structure. 

 Both these competent investigators and Zopf, who observed a similar 

 object in Amoebochytrium, noted that a pore developed in it through 

 which the zoospores passed and that it was not dehisced. 



Endoopercula (see p. 63) have recently been observed in species 



