are rather evenly and closely spaced within a wide gelatinous in- 

 vestment; cells l.S-2.2fx in diameter, cell contents pale blue-green 

 or gray-green, homogeneous; colony 16-18^ wide. 



The small size of both the cells and the colony help in identifica- 

 tion. 



Very common in acid habitats and invariably found in association 

 with desmids. Mich., Wis. 



Merismopedia Trolleri Bachmann 1920, p. 350 

 PI. 101, Fig. 5 



A colony of 8-16 spherical cells, each with a distinct sheath and 

 evenly arranged within a transparent colonial mucilage; cell con- 

 tents with pseudo vacuoles (gas vacuoles ?), appearing brownish or 

 purplish because of light-refraction; cells 2-3.5/^ in diameter. 



Uncommon; in plankton and among other algae in tychoplankton; 

 and in Sphagnum bogs. Wis. 



Judging from Lemmermann's description of M. Marssonii it is 

 not diflFerent from M. Trolleri except in its smaller size, a character 

 which is insufficient to separate the two species. M. Trolleri has 

 been reported previously in this country by Prescott and Croasdale 

 (1937), from Massachusetts. 



HOLOPEDIUM Lagerheim 1883, p. 42 

 Cells subglobose to subcyhndric, or ellipsoid, either closely or 

 somewhat distantly arranged to form flat plates which are quadrate, 

 or subquadrate and lobed, the cells forming linear series in part, 

 but in general irregularly disposed. 



The cells appear round when seen on end, but appear elongate 

 and subcyhndric when seen from the side, especially in H. Dieteli 

 (Richter) Migula, a species not reported from this country. 



Holopedium irregulare Lagerheim 1883, p. 43 

 PI. 107, Figs. 10, 11 

 Cells subcyhndric, irregularly arranged in flat plates, with long 

 axes mostly parallel, contents pale blue-green; cells 2-3/a in diameter. 

 Tychoplankter. Found in acid lakes. Mich. 



SYNECHOCOCCUS Naegeh 1849, p. 56 

 A cylindrical oblong, or elliptical unicell; or sometimes 2 to 4 

 cells seriately united as a result of cell division in one plane; free- 

 floating, without a sheath; cell contents pale blue-green or some 

 shade of yellow, highly granular. 



[460 ] 



