482 Smith: ALGAE FROM THE LAKES OF WISCONSIN 
PLATE 26, FIG. 27 
DistriBuTion: plankton, Birch, Soft and Tamarack Lakes. 
The species resembles A. macrospora Klebh. in the general 
appearance of the trichome, but the cellular dimensions are quite 
different, since the cells of A. macrospora are much smaller and the 
spores proportionally larger. 
Lyngbya Birgei sp. nov. 
Filaments free-floating, straight, rarely curved. Sheath firm, 
hyaline, homogeneous. Trichomes not constricted at cross walls, 
ends rounded but not attenuated. Cells shorter than broad, with 
many ‘‘gas vacuoles” at times. 
Filaments 24-20 u wide; trichomes 22-18 uw wide. 
PLATE 26, FIG. 28 
DIsTRIBUTION: plankton, Kegonsa, Mendota, Monona, Ocono- 
mowoc, Squirrel and Waubesa Lakes. 
Almost all of the true plankton species of Lyngbya have fila- 
ments that are less than 5 win diameter. The only other plankton 
species of any size is L. Hieronymusii Lemm., but the Wisconsin 
Lyngbya is much larger. This species is found in abundance in the 
Madison lakes and at times has been the major constituent of the 
“blooms” that have appeared in these lakes. This is especially 
the case in Lake Kegonsa. The cell contents at such times are 
very characteristic of ‘‘bloom’’—producing Myxophyceae, since 
there are large numbers of reddish ‘gas vacuoles” in each cell. 
The species is named after Mr. E. A. Birge, Director of the State 
Survey. 
THE UNIVERSITY OF WISCONSIN 
