212 Minnesota Algae 



(2) Filaments 25 mic. in diameter S. azureum 



3 Plants living on soil, rocks, or bark, not submerged 



(i) Filaments 7-15 mic. in diameter S. hofmanni 



(2) Filaments 9-15 mic. in diameter S. varium 



(3) Filaments 12-15 mic. in diameter S. javanicum 



(4) Filaments 10-18 mic. in diameter S. ocellatum 



(5) Filaments up to 20 mic. in diameter S. intertextum 



(6) Filaments 15-20 mic. in diameter S. austinii 



(7) Filaments 15-21 mic. in diameter; cells compressed 



S. millei 



(8) Filaments 15-21 mic. in diameter; cells somewhat quadrate or 



elongate S. guyanense 



(9) Filaments 19-24 mic. in diameter S. amplum 



(10) Filaments 20-25 mic. in diameter S. woUeanum 



(11) Filaments 16-30 mic. in diameter S. stuposum 



II Sheaths lamellose, with diverging layers; plants usually living on soil 



or rocks, not submerged. 



1 Filaments 10-15 ""ic. in diameter S. tolypotrichoides 



2 Filaments 12-18 mic. in diameter S. flavo-viride 



3 Filaments 15-21 mic. in diameter S. mirabile 



4 Filaments 18-36 mic. in diameter S. myochrous 



5 Filaments 40-75 mic. in diameter S. badium 



III Sheaths thick, lamellose, forming wings or membranaceous expan- 



sions (ocreae); branches in basal portion of filament issuing in 

 pairs, those in the upper portion solitary. 



1 Plants living in water 



(i) Plants living in salt water; filaments 28-50 mic. m diameter 



S. fuliginosum 



(2) Plants living in fresh water, on dripping rocks or submerged 



S. alatum 



2 Plants' living on damp rocks or en bark 



(i) Filaments 12-16 mic. in diameter S. jimipericolum 



(2) Filaments 15-30 mic. in diameter S, crustaceum 



(3) Filaments 24-40 mic. in diameter S. densum 



Species not well understood 



S. bornetianum 

 S. dubium 

 S. hirtulum 

 S. immersum 

 S. polymorphum 

 S. rubrum 

 S. simplex 



