IOWA ACADEMY OF SCIENCE 
57 
„ Subfamily II. 
Lyngbyeae. 
KEY TO THE GENERA. 
Trichomes consisting of many cells. 
Filaments simple; sheaths firm, apices of trichomes straight 
1. Lyngbya 
Filaments simple; sheaths thin, always hyaline, mucous and more or 
less diffluent, in some species absent, apices of the trichomes commonly 
curved. 
Trichomes more or less agglutinated by their mucous sheaths; cells of 
the trichome often separated by a thin mucous layer .... 2. Phormidium 
Trichomes destitute of sheaths, free, straight or with curved ex- 
tremities 3. Oscillatoria 
Trichomes consisting of one cell, twisted into a regular spiral 
4. Spirulina 
1. Lyngbya. 
26. L. vulgaris (Kuetz) Kirch. 
Iowa City. Hobby. 
Grinnell. Damp Soil. Fink. 
27. L. ochracea (Kuetz) Thur. 
Iowa City. Hobby. 
Eagle Grove. In the trough of a flowing well. It is found very com- 
monly in the waters in this locality that are laden with iron, the sheath 
becoming impregnated with this substance. Buchanan. 
28. L. obscyra. Kuetz. 
Eagle Grove. A pond amid bladderwort. Buchanan. 
29. L. subtorulosa (Breb.) Wolle. ( Phormidium lacustre Naeg.) 
Iowa City. Hobby. 
80. L. cataracta (Rabenh.) Wolle. ( Phormidium cataractum Rab.) 
Iowa City. Hobby. 
81. L. glutinosa Ag. ( Phormidium glutinosum A Br.) 
2. Phormidium. 
82. P. tenue (Menegh) Gomont. 
Fayette. Frequent. Fink. 
Ames. On pots in greenhouse. Buchanan. 
Ames. Pond. Buchanan. 
Eagle Grove. In pond among decaying rushes. Buchanan. 
Eagle Grove. Bottom of the margin of the slough. Buchanan. 
3. Oscillatoria. 
KEY TO THE SPECIES. 
Filaments very narrow, divisions often not evident. 
Filaments .6 u in diameter 0. angustissima 
Filaments 1.8-2.5 u in diameter O. tenerrima 
Filaments broader, articulations usually distinct. 
Articulations about half as long as wide. 
