194 Minnesota Algae 



Plate IX. fig. 20. 



Plant mass gelatinous, dark green; trichomes 4.2-6 mic. in diameter, 

 with rotund apical cells; cells barrel-shaped, equal to the diameter in length, 

 or a little shorter or longer; heterocysts 6-8 mic. in diameter, spherical, 

 or 6 mic. in diameter and 10 mic. in length, ovoid; gonidia 8-10 mic. in 

 diameter, 20-40 mic. in length, when young ovoid, finally becoming espe- 

 cially cylindrical, solitary or in series, with rounded apices, contiguous to 

 the heterocysts, developed centripetally; wall of gonidium smooth, in ma- 

 ture specimens very pale soot-colored. 



Massachusetts. On dead leaves, in swamp near Bear's Den Path, Middle- 

 sex Fells. (Collins). Wood's Hole. (Humphrey and Miyabe). In still water. 

 West Falmouth. August 1896. (Humphrey). Rhode Island. Roger 



Williams Park. (Bennett). Connecticut. Pool below Factory Pond, 



Bridgeport. (Holden). New Jersey. In brackish ditches. (Wolle). 



Pennsylvania. "In a dark little grotto, formed by shelving rocks." Reading 

 Railroad, just above the Flat Rock tunnel; on wet ground by a horse-trough, 

 near west end of upper bridge at Manayunk; on banks of Schuylkill River, 

 in vicinity of Philadelphia. (Wood). On dripping rocks and on wet ground. 

 (Wolle). Ohio. (Kellerman). Illinois. Evanston. (Johnson). Min- 

 nesota. Second Creek, Lake City, Wabasha County. September 1894. 

 South Dakota. In a slough. Elm River, eight miles north of Aberdeen. May 



1896. (Griffiths). Nebraska. In a small creek near Lincoln. (Saunders). 

 Montana. Helena. (Kelsey). Washington. On moist bank near bicycle 

 path. Madrona Park, Seattle. May 1901; floating on pools and lakes, or 

 on moist ground, Coupeville, Whidbey Island; Port Townsend. (Gardner). 

 California. San Francisco. (Setchell). 



Var. elongata (Kuetzing) Bornet and Flahault. 1. c. 236. De Toni. 1. 

 c- 453- 



Tilden. American Algae. Cent. III. no. 293. 1898. 



Heterocysts 7-9 mic. in diameter, very long, 6-18 mic. in length; go- 

 nidia up to 70 mic. in length. 



South Dakota. Floating in stagnant water on prairie. Columbia. June 



1897. (Griffiths). 



Var. stenospora Bornet and Flahault. 1. c. 236. De Toni. 1. c. 454. 

 Tilden. American Algae. Cent. II. no. 172. 1896; Cent. VI. no. 577. 1902. 

 Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 31. no. 1506. 1908. 



Trichomes more slender; apical cell acute conical; gonidia S-io mic. in 

 diameter, 16-40 mic. in length, often two to eight in a chain; wall of go- 

 nidium smooth, colorless. 



Massachusetts. Forming rather thin films on plants and boards in a 

 ditch. Eastham. August 1908. (Collins). Minnesota. Floating on surface 

 of shallow pool on sandy or muddy beach. Minnesota Point, Duluth. August 

 1901. Colorado. On aquatic plants in slowly flowing stream in swamp. 

 Five miles southeast of Port Collins. July 1896. (Cowen). 



