192 AQUA TIC PH YCOM YCETES 



MICROMYCES Dangeard, emend. 1 



Le Botaniste, 1: 55. 1889 



(Fig. 16 A-E, H, p. 196) 



Micromycopsis Scherffel, Arch. Protistenk., 54: 202. 1926. 



Synchytrium subgenus Microsynchytrium Karling, Mycologia, 45 : 279. 1953. 



Thallus at first naked, somewhat amoeboid, later walled, endobiotic, 

 holocarpic, without a specialized vegetative system, forming the rudi- 

 ment of the prosorus or resting spore; prosorus thick- walled, spiny 

 or smooth-walled; sorus simple or compound, formed as a direct 

 outgrowth of the prosorus or at the tip of a discharge tube, if simple, 

 dividing into a variable number of inoperculate, uni- or multiporous, 

 smooth or spiny, thin- or somewhat thick-walled angular sporangia 

 not enclosed in a common soral wall which give rise directly to zo- 

 ospores, if compound, dividing into sporangia which give rise to spher- 

 ical, amoeboid, occasionally unifiagellated primary zoospores, each 

 of which after encystment produces a few minute secondary zoospores; 

 zoospores minute, posteriorly uniflagellate; resting spore thick-walled, 

 upon germination functioning as a prosorus., 



For some time it has been increasingly evident from the investi- 

 gations of Canter (1949c), Rieth (1950a), and others that the distinc- 

 tions between Micromyces and Micromycopsis were breaking down 

 (Sparrow, 1932b). Future work is expected to reveal new forms which 

 will further obliterate any remaining differences between them and 

 will sustain this merger. 



Canter's (1949c) excellent series of observations on these curious 

 endophytic algal parasites confirmed beyond question the formation 

 of two kinds of sori: one, the usual chytridiaceous simple type whose 

 sporangia give rise directly to zoospores, and another, a more com- 

 plex type whose soral segments produce feebly moving, often poste- 

 riorly uniflagellate structures. These soon encyst and give rise to active 

 zoospores which presumably infect new host plants. Canter calls the 

 amoeboid bodies produced by the second type of sorus "primary zoo- 

 spores," and the motile bodies derived from it "secondary zoospores." 

 Since the soral segments give rise to what are functionally sporangia 



See Rieth (1956a) for a synopsis of this genus. 



