IOWA ACADEMY OF SCIENCE 
59 
Eagle Grove. Floating in Hewitt’s Pond. Buchanan. 
39. O. froelichii var. fusca Kirch. 
Ames, la. On moist soil in the greenhouse. Buchanan. 
40. O. princeps Vauch. 
Fayette. Fink. 
Eagle Grove. Pond, amid dense growth of Lemna. Buchanan. 
41. O. imperator Wood. 
The largest species of oscillaria that is to be found in the state. 
Ames. Bessey. 
4. Spirulina. 
42. S. major Kutz. 
Ontario. Slough, amid Lemna trisulca. Buchanan. 
Suborder II. 
Trichophoreae. 
KEY TO FAMILIES. 
I. Trichomes attenuated from the base to the apex, which is piliferous; 
heterocysts basal, rarely absent Rivulariaceae 
II. Trichomes attenuated from the middle toward each extremity. Hetero- 
cysts absent Camptotrichaceae 
Family I. 
Rivulariaceae. 
KEY TO THE GENERA. 
Filaments free, simple or falsely branched, branches distinct and free 
1. Calothrix 
Filaments forming a hemispherical or globular thallus, closely united by mucus. 
Filaments radiately disposed in a tough globose or hemispherical attached 
thallus. Spores unknown 2. Rivularia 
Filaments radiately disposed in a soft globose free floating thallus. Spores 
regularly produced 3. Gloeotrichia 
1. Calothrix (Mastigonema) . 
43. C. elongatum (Wood). 
Ames. Bessey. 
-4-4. C. parietina (Naeg.) Thur. 
Ontario. On stem of Phragmites. Buchanan. 
2. Rivularia. 
No species of Rivularia as at present recognized has been found in the 
state, the species reported by Bessey as R. cartilaginea is probably Gloeo- 
tricha jtisum. 
3. Gloeotricha. 
4-5. G. Pisum Thur. 
One of the most abundant of the algae in some of the lakes at certain 
seasons of the -year. 
Iowa City. 1880. Hobby. 
Ames. 1884. Bessey. 
