Tilden: LIST OF FRESH-WATEK ALGAE. 27 



Grown in aquarium in which water was saturated with 

 nitrous oxide. University of Minnesota, Minneapolis, 

 Minnesota. Emil Sandsten. February 23, 1898. 



RIVULARIACEAE RABENHORST Fl. Eur. Algar. 2: 2. 1865. 



250. Calothrix parietina (NAG.) THUR. Ess. Class. Nostoch. 



in Ann. Sci. Nat. Bot. VI. I : 381. 1875. 

 On stone sides of fountain, breaking up in small frag- 

 ments when peeled off. Kenwood, Minneapolis, 

 Minnesota. August 3, 1895. 



251. Dichothrix calcarea TILDEN Am. Alg. Cent. II. no. 165. 



1896. Bot. Gaz. 23 : 95-104. pi. 7-9. F. 1897 

 Forming a part of the lime incrustation which covers 

 sides of wooden tank. With no. 240. Minneapolis, 

 Minnesota. October i, 1895. 



252. Rivularia biasolettiana MENEGH. in Zanardini Syn. 



Alg. in mari Adriatico collect, in Reale Acad. Sci. 

 Torino. II. IV. 42. 1841. 



On rocks at edge of lake. Big Stone lake, Dakota. 

 Coll. David Griffiths. October 4, 1895. 



253. Gloeotrichia pisum (Ac.) THURET. Essai de class. 



Nostochinees in Ann. Sci. Nat. Bot. VI. i : 382. 



, l8 75- 



Floating on surface of water in large quantity. Lake 

 Minnewaska, Glenwood, Minnesota. Coll. Elizabeth 

 H. Foss. August, 1897. 



NOSTOCEAE KUTZ Phyc. gen. 203. 1843. 



254. Anabaena azollae STRASB. Bot. Prakt. 341. f. 130. 



1887. 



In chambers in the leaves of Azolla Caroliniana. Uni- 

 versity plant-house, Minneapolis, Minnesota. Sep- 

 tember 15, 1896. 



255. Anabaena cycadearum REINKE, Bot. Zeit. 37: 473- 



476. pi. 6. f. 1-5. 1879. 



In roots of Cycas revoluta. University plant-house, 

 Minneapolis, Minnesota. December 20, 1896. 



256. Anabaena flos-aquae (LYNGB.) BREB. in Brebissonet 



Godey. Algues des environs de Falaise. 36. 1835. 

 Floating in abundance on surface of water. Cedar 



