Lake Maxinkuckee, Physical and Biological Survey 145 



On July 28 it was still scarce. By August 8 it was abundant, a 

 large quantity being obtained in a towing in Outlet Bay. It was 

 noted again on the 16th. On August 21, on a visit to Winona Lake, 

 a towing was made and it was observed that filaments there were 

 longer and more abundant than at Lake Maxinkuckee. On Sep- 

 tember 28 the plankton taken in Outlet Bay was a dirty brown 

 fibrous mass, composed mainly of the empty sheaths of the fila- 

 ments of this species, the interior cells having mostly escaped to 

 make new independent colonies or filaments. By noon of the same 

 day the quantity of this species had so greatly increased in the lake 

 that it was evident to the eye. On September 5 it was still form- 

 ing hormogonia. 



The stomach of a small painted turtle examined in Septem- 

 ber, 1906, contained Lyngbya in such quantities that it must have 

 been taken in intentionally, although it is difficult to explain where 

 the turtle had obtained so much. Examinations of the stomachs of 

 these turtles have shown that they partake largely of various algse; 

 indeed, algae seem at times to furnish the turtles' main diet. 



The rapid increase of Lyngbya during the late summer and 

 early autumn months is due to its excessively rapid reproductive 

 process which is simply the slipping out of short portions of fila- 

 ments and occasionally single disc-shaped shells from the sheaths of 

 the old filaments. 



We know little about the part this species plays in the economy 

 of the lake. It never appears, even in its greatest abundance, to 

 become a positive nuisance. Entomostraca may, and mussels do, 

 feed upon the shorter filaments, but the longer filaments are un- 

 handy for most of the plankton-consuming organisms except the 

 painted turtle. 



18. APHANIZOMENON FLOS-AQU^ (Linnaeus) 



On August 4, 1906, some was taken with the No. 2 towing- 

 net in front of the ice-office. Taken also in Lost Lake, but it does 

 not appear to be common. 



This is the most common plankton element in some of the lakes 

 of Minnesota and is abundant at times in the upper Mississippi. 

 The waters of reservoirs sometimes seem almost thickened with it. 



19. ANAB^ENA FLOS-AQU.^ Biebisson 



This is the most abundant plankton species of the lake, it 

 having been taken in almost every haul of the plankton net during 

 1899 and 1900. 



During 1900 and 1901 plankton-scum quite frequently accumu- 



10--17618— Vol. 2 



