284 Minnesota Algae 



Species not well understood 



R. mexicana 

 R. microscopica 

 Z minutula 

 Z. mollis 



518. Rivularia pisum Agardh. Syst. Algar. 25. 1824. Bornet and Flahault. 

 Revis. des Nostoc. Ann. Sci. Nat. Bot. VII. 4: 366. 1886. (Gloeo- 

 trichia pisum Thur.). De Toni. Syll. Algar. 5: 653. 1907. 



Wood. Contr. Hist. Fresh-Water Algae North America. 47. pi. 2. f. 9. 

 1872. (R. cartilaginea Wood). WoUe. Fresh Water Algae. II. 

 Bull. Torr. Bot. Club. 6: 138. 1877. Campbell. Plants of the Detroit River. 

 Bull. Torr. Bot. Club. 13: 93. 1886. (R. echinata Eng. Bot). Arthur. 

 Some Algae of Minnesota supposed to be Poisonous. Fourth Bien. Report 

 Bd. Regents. Suppl. i. 99. 1887; Second Report on some Algae supposed 

 to be Poisonous. 1. c. 109. 1887. (G I. pisum (Ag.) Thur.). Collins. 

 Algae of Middlesex County. 13. 1888. Wolle and Martindale. Algae. 

 Britton's Catalogue of Plants found in New Jersey. Geol. Surv. N. J. 2: 

 604. 1889. Anderson and Kelsey. Common and Conspicuous Algae of 

 Montana. Bull. Torr. Bot. Club. 18: 143. 1891. Saunders. Protophyta- 



Phycophyta. Flora of Nebraska. 25. pi. 3. f. 33. 1894. Collins, Holden 

 and Setc'hell. Phyc. Bor.-Am. Fasc. 7. no. 311. 1897. Tilden. List of 



P"resh-Water Algae collected in Minnesota during 1896 and 1897. Minn. 

 Bot. Studies. 2: 27. 1898. Kellerman. Proposed Algological Survey of 

 Ohio. Ohio Nat. 2: 222. 1902. Nelson. Observations upon some Algae 

 which cause "Water Bloom." Minn. Bot. Studies. 3: 52, 56. 1903. Collins. 

 Phycological Notes of the late Isaac Holden. — II. Rhodora. 7: 238. 1905. 

 Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 27. no. 1310. 1905. 



Plate XIX. fig. 6. 



Colonies small, 1-2 mm., rarely up to i cm. in diameter, spherical, hard, 

 blackish green; filaments crowded; trichomes 4-7 mic. in diameter, ending 

 in a hair; cells somewhat quadrate; cell contents olive; gonidia 9-1S mic. 

 in diameter, 60-400 mic. in length, surrounded by a special sheath. 



Massachusetts. Medford, Newton. (Farlow). On stems of flowering 

 plants. Lake Quannapowitt, Wakefield. September 1906. (Collins). Con- 

 necticut. Floating on the surface, forming a verdigris-green scum. Twin 

 Lakes, Salisbury. October 1892. (Setchell and Holden). New Jersey. 

 "Parasitic" on aquatic plants in ponds and pools. (Wolle). Ohio. (Kel- 

 lerman). Michigan. Attached to leaves of water plants in marsh. North- 

 ern part of state. (Wood). Grosse Isle, near mouth of Detroit River. Sum- 

 mer of 1885. (Campbell). Minnesota. Lake Phalen, near St. Paul. August 

 1882; Lake Tetonka, at Waterville. July 1883; Lake Minnetonka. August 

 1883. (Farlow and Arthur). Abundant on water plants. Vermilion Lake. 

 July 1886. (Arthur, Bailey and Holway). Floating on surface of water in 

 large quantity. Lake Minnewaska, Glen wood. August 1897. (Foss). Iowa. 

 On Utricular! a. East Okoboji Lake. July 1883. (Farlow and Arthur). 



