AVooil.] ^ -'^ [June 18, 



BemarTis. — Our American form does not quite equal the measurements 

 given by Eabenliorst. I have never measured it over ^-^q-^" in diameter. 



o. LiMOSA. {Roth.) Agli. 



Hab. In stagnis proj)e Pliiladelphia. 



Bemarks. — The dissepiments are never granulate, at least that I have 

 seen. Otherwise our American forms agree in all respects with the de- 

 scriptions of the European. 



O. NEGLECTA. Sj)- JVoV. 



O. trichomatibus niodice brevibus, aut dilute purpuraceo-plumbeis aut 

 plumbeo-cinereis, plerumque rectis, aut stratum mucosum atro-purpureum 

 hand distincte radiante formautibus, aut in strato gelatinoso liaud 

 radiante subplumbeo dispersis et cum algis aliis intermixtis, rare oscil- 

 lantibus sed lente sese moventibus ; articulis diametro fere 4 plo bre- 

 vioribus ; dissepimentis plerumque hand granulosis, rare indistincte 

 granulosis ; apiculo obtuse rotundato, interdum breve nonnihil atten- 

 uato. 



Filaments rather short, of a dilute purplish lead color, or leaden gray, 

 generally straight, either forming a mucous, blackish purple stratum 

 without marked rays, or diffused with other algae in a gelatinous mass, 

 rarely oscillating but gliding ; articles about four times shorter than bi'oad ; 

 joints for the most part not granulate, rarely indistinctly granulate ; ends 

 obtusely rounded, occasionally shortly somewhat attenuate. 



Diam. jJ-^j^"=.Q066. 



Hab. In stagnis prope Philadelphia. 



O. IMPERATOR. Sj). NoV. 



O. in strato mucoso, plerumque natante, olivaceo-atro, longe radiante ; 

 trichomatibus rectis aut subrectis, tranquillis, dilute viridibus vel satu- 

 rate olivaceis, baud oscillantibus, sed ambulantibus ; apiculis nonnihil 

 attenuatis, late rotundatis vel subtruncatis, curvatis ; articulis diametro 

 0-12 plo brevioribus, ad genicula indistincte contractis ; cytioplasmate 

 homogeneo, olivaceo-viride ; vaginis firmis, ad genicula distincte trans- 

 verse striatis, 



O. Occurring in an olive-black mucous stratum, mostly swimming and 

 with long raj) s ; filaments straight or straightish, light green or deep 

 olive, tranquil, not oscillating, but moving with a gliding motion ; ends 

 somewhat attenuate, broadly rounded or subtruncate, curved ; articles 

 5-12 times shorter than broad, slightly contracted at the joints ; cytio- 

 plasm homogeneous, olive green j sheaths firm, distinctly transversely 

 grooved at the joints. 



Diam. .002." 



GEN. LYNGBYA. 



I,. BICOLOR. Sp. Nov. 



L. trichomatibus simplicibus in ctespites nigro-virides dense in- 

 tricatis, varie curvatis, plerumque inarticulatis, interdum breve articu- 



