194 AQUATIC PHYCOMYCETES 



it is the opinion of this writer that the differences indicated in the 

 generic key are of sufficient import to warrant the maintenance of 

 Micromyces. 



KEY TO THE SPECIES OF MICROMYCES 



Prosorus spiny-walled 



Spines of prosorus scattered 



Sori typically sessile, smooth-walled 

 Spines slender, up to 7.5 a long 



Zoospore spherical, 1 \x in diameter M. zygogonii, p. 195 



Zoospore fusiform, 6 by 2 jj. M. petersenii, p. 198 



Spines up to 22 \j. in length M. longispinosus, p. 198 



Sori typically formed at the orifice of a discharge tube 

 Sporangia ten to one hundred; sorus covered with low, 

 coarse blunt spines, divided into polygonal areas 



M. mirabilis, p. 199 

 Sporangia four to six in number; sorus covered with minute 



blunt spines, divided radially M. intermedia, p. 200 



Spines of prosorus seriate or helically seriate 



Spines of prosorus typically senate in rings; sorus simple, 

 smooth- walled; sporangia tetrahedral, sessile 



M. ovalis, p. 200 

 Spines of prosorus typically helically seriate; sorus compound, 

 spiny, usually formed at the orifice of a discharge tube; 

 sporangia spherical 

 Prosorus 13-16 \l by 18-20 \l; sorus covered by blunt spines 



M. cristata var. cristata, p. 201 

 Prosorus 8.5-10.4 \i\ sorus covered by sharp spines 



M. cristata var. minor, p. 201 

 Prosorus smooth-walled 



Sorus smooth-walled, simple or compound 



Sorus simple, sessile or rarely at orifice of a tube; sporangia 



tetrahedral, zoospores numerous M. laevis, p. 202 



Sorus compound, typically formed at the orifice of a tube; spo- 

 rangia spherical, zoospores few (two to six) M.fischeri, p. 202 

 Sorus spiny-walled, simple 



Sorus composed of three tetrahedral sporangia 



M. zygnaemicola, p. 203 

 Sorus composed of seven to fifteen pyramidal segments 



M. oedogonii, p. 203 



