Myxophyceae 37 



Genus CLATHROCYSTIS Henfrey 

 Mic. Journ. 53. pi. 4. f. 28-36. 1856. 



Colonies of variable shape, at first solid soon becoming saccate and 

 clathrate, ("fragments of the broken fronds occurring in irregularly lobed 

 forms"), surrounded by a colorless, gelatinous, indistinctly limited integu- 

 ment; cells spherical, numerous. 



I Cells 3-4 mic. in diameter, spherical. C. aeruginosa 



II Cells 6-9 mic. in diameter, spherical or oval C. robusta 



8g. Clathrocystis aeruginosa (Kuetzing) Henfrey. Mic. Journ. 53. pi. 4. f. 

 28-36. 1856. De Toni. Syll. Algar. 5: 94. 1907. 

 Wolle. Fresh-Water Algae U. S. 327. pi. 210. f. 17, 18. 1887. Collins. 

 Algae of Middlesex County. 16. 1888. Bennett. Plants of Rhode Island. 

 115. 1888. Jelliffe. A Further Contribution to the Microscopical Examina- 

 tion of the Brooklyn Water Supply. Brook. Med. Journ. 8: 592. 1894. 

 Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 2. no. 51. 1895. Col- 

 lins. Algae. Flora of the Blue Hills, Middlesex Fells, Stony Brook and 

 Beaver Brook Reservations of the Metropolitan Park Commission, Massa- 

 chusetts. 126. 1896. Tilden. List of Freshwater Algae collected in Minne- 

 sota during 1895. Minn. Bot. Studies, i: 599. 1896; American Algae. Cent. 

 II. no. 194. 1896. Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 24. 

 no. 1153. 1904. Buchanan. Notes on the Algae of Iowa. Proc. Iowa 

 Acad. Sci. 14: 9. 1908. 



Plate II. fig. 21, 22. 



Plant mass a bright green scum, floating in vast strata on freshwater 

 pools, presenting to the naked eye a finely granular appearance, when dried 

 appearing like a crust of verdigris; colonies spherical or elongate, solid, 

 soon becoming saccate and clathrate; cells 3-4 mic. in diameter, spherical, 

 very numerous embedded in a colorless integument. 



United States. Often floating in large strata as a glaucous green scum 

 on fresh water pools. (Wolle). Massachusetts. Horn Pond, Woburn. 

 (Farlow). Spot Pond, Stoneham; forming a floating scum on Middle 

 Reservoir. Middlesex Fells. (Collins). Rhode Island. Common, at times 

 abundant. (Bennett). Mashapaug Pond, Providence. October 1892. (Oster- 

 hout). New York. Brooklyn water supply. (Jelliffe). Minnesota. 



Covering surface of lake in sheltered bays and around edges, sometimes 

 to a depth of three inches. In decaying forms a milky white, ill-smelling 

 scum. Long Lake, Hennepin County. September 1895. (Shaver and Tilden). 

 On bottom at edge of lake in very small round bunches or flat patches, 

 fragile. Como Park, St. Paul. August 1895. (Tilden). Halsted's Bay, 

 Lake Minnetonka. November 1906. (Hill). Minneapolis city water (Cor- 

 bett). Iowa. Ames. 1884. (Bessey). East Okoboji Lake. October 1904. 

 (Buchanan). Washington. Floating in Green Lake. Seattle. December 

 1903. (Gardner). 



"The smallest fronds met with are usually roundish or ellipsoidal. 

 When quite young they appear to be solid, but as they grow by the multi- 

 plication of the internal cells and the secretion of gelatinous matter, the 



