TJie Diatoms of Nebraska 37 



Mcloseira Ag. Syst. Alg., p. 14. 1824. 



Cells spherical to cylindrical, closely united in filaments; valve 

 view circular, simply punctate. Chromatophores small rounded or 

 irregular plates which are distributed irregularly on the wall of the 

 cell. Auxospore formation asexual. One enlarged daughter cell 

 is produced from one mother cell ; cell axis of the daughter cell is 

 parallel or perpendicular to that of the mother cell. In the first 

 case the daughter cell remains within the mother cell and separates 

 the mother chain. 



A. Junction surfaces of the cells convex. i. L. varians. 



AA. Junction surfaces of the cells plane, often denticulate. 

 h. Cells with a sulcus near the sutural margin. 



c. Length of the cells usually not much greater than the width; 



with distinct granules. 2. L. distans. 



cc. Length of the cells usually greater than the width ; with fine 

 granules. 3. L. crcnulatiim. 



bb. Cells without a sulcus on each side of the connecting zone. 



4. L. granulatum. 



I. Lysigonium varians (Ag.) D. T. Alg. Alg. Abyss. i8pi. 



Mcloscira varians Ag. Consp. 18^0. 



PI. I, figs. 1-5. 



Cells in pairs ; ends of cells convex, covered with fine puncta 

 between which are some coarse dots; sides of cells with fine puncta 

 intermixed with some coarser dots, with a row of coarse beads near 

 the margin ; connecting zone between two cells finely striate. 

 Sporangial cells almost globular (figs. 3-5). Diameter 8-35^. 

 A form 4-5 fi in diameter seems to belong to this species. 



In creeks, rivers, ponds, ditches, lakes, etc. Andrews, .-XHselmo, Burgc, 

 C'allaway, Cedar Creek, Central City, Cody Lake, Crawford, Dismal River, 

 Dunning, Emerald, Emmett, Gordon Creek, Grand Island, Hackberry 

 Lake, Halsey, Hyannis, Ithaca, Lakeside, Lincoln, Long Pine, Melia, Mil- 

 ford, New Helena, Newport, Norfolk, Orella, Pelican Lake, Red Cloud, 

 Ruby, Seward, South Bend, St. Michael, St. Paul, Stanton, Tekamah. 

 Thedford, Va'entine, West Point, Whitman. 



Fossil : Agate, Greeley County, Hay Springs, Loup City, Merriman, Spald- 

 ing, Thedford, Williams's Canyon. 



Chippewa Falls, Wis. ; Blackpipe, Conata, Little White River, Rapid City, 

 S. Dak. ; Stockton, Cal. ; Blackhand, Granville, New Concord, Put-in Bay, 

 Ohio. 



