Smifh—Algae Found in Wisconsin Lakes 643 
emend., P. clathratum (Schrot) Lemm., P. Sturmii Reinsch, and 
P. ovatum (Ehrenb.) A. Br. 
One horned forms were sufficiently common in the plankton 
catch from Vermilion lake to afford ample material for studying 
the range of variation. The typical P. simplex cells have con¬ 
cave sides and no, or very small, intercellular spaces between 
them. I have never observed this condition in any of the Wis¬ 
consin material, the intercellular spaces always being as large 
as the cells. This form is commonly called P. clathratum 
(Schrot.) Lemmermann, but since it differs from the typical P. 
simplex in the same manner that’the varieties clathratum and 
reticulatum differ from P. duplex Meyen there is no reason for 
considering it a distinct species. Bailey ^s figures of Monactinus 
duodenarius is so clear cut that there is no doubt but that P. 
clathratum is identical with it. 
The punctation or granulation of the wall is so variable that 
it cannot be used for distinguishing varieties; while those var¬ 
ieties based upon arrangement of the interior cells of the coe- 
nobe are also worthless. (Plate 13, fisg. 1--5). 
II. Camp (rr), Mary (rrr), Silver (rr). 
III. Bear (r), Eice (r). Vermilion (cc). 
Pediastrum boryanum (Turp.) Menegh. 
Linnaea 14: 210. 1840; G. S. West, Brit. Preshw. Algae 211. figs, 85F-85H. 
1904. , 
II. Browns (rr). Camp (s), Center (s), Eagle (sss), Elizabeth ' (ss). 
Green (rrr), Hooker (rr), Mary (ss). Mill (rrr), Paddock (rrr), 
Silver (r). 
III. Bear (ss), Beaver dam (ss), Chetac (rrr), Chetek (rrr). Granite (rrr). 
Grindstone (rr). Horseshoe (ss). Lac Court Oreilles (rr), Owen 
(r), Prairie (rrr), Pokegama (rrr), Eeserve (rr), Eice (rr). Ver¬ 
milion (rr), Whitefish (rr). 
Pediastrum GLANDULiFERUM Bennett. 
Jour. Eoy. Micr. Soc. 1892: 7. pi. 2, figs. 5-7. 1892. 
III. Horseshoe (rrr). 
Pediastrum araneosum (Racib.) G. M. Smith. 
Bull. Torr. Bot. Cl. 43: 476. 1916. 
III. Horseshoe (rr). 
