Lake Maxinkuckee, Physical and Biological Survey 139 



great number of turtles that dwelt among them. Some of the alga? 

 are to be found the year round, especially where there are springs 

 which keep the water abnormally warm. Others as Draparnaldia 

 (which is rare in the lake) and the diatoms thrive more in cold 

 water and appear in the greatest abundance during the winter. 



The coarser filamentous alga? function in the lake as the higher 

 plants do, i. e., they help oxygenate the water and serve as food and 

 shade for fishes. Various insect larva? and probably most of the 

 smaller herbivorous fishes, as well as some species of turtles, use 

 them for food. At times they, along with fragments of larger 

 plants, are washed upon the shore where they decay, forming a 

 soft black mud. 



More important, but generally less conspicuous, are the minute 

 alga? barely visible to the naked eye and including many of the blue- 

 green colonial forms, the diatoms, desmids, etc. By far the greater 

 number of these minute forms, like the coarser alga?, stay near 

 shore, either because they are attached to or generally more or less 

 entangled, among other growths, or, to sum up all in one sen- 

 tence, because they find the best conditions for life there. These 

 are the so-called limnetic forms. Others, however, stray far out 

 from shore and are driven hither and thither by the winds, waves 

 and currents ; these form the vegetable part of the plankton or 

 phyto-plankton and affect the lake in various ways. They give 

 the water, in a certain sense, its optical quality, just as minute 

 specks of dust and motes give the air what might in an artistic 

 sense be called its "atmosphere" — its blueness or grayness and so 

 on. Moreover it is upon these plankton alga? that the newly hatched 

 fish all feed, either directly or indirectly, by feeding upon the small 

 animals that feed upon it; and again when the plankton alga? be- 

 come too abundant they rise to the surface and form a disagree- 

 able and ill-smelling scum which appears to affect some people who 

 "go swimming in dog days" much as a mild case of ivy poisoning 

 might. And they render the water of some reservoirs so rank and 

 unpalatable that they become a nuisance for which dosage of the 

 affected water with copper sulphate was devised as a remedy. 



The free floating forms of alga? were collected by means of va- 

 rious sorts of plankton nets, one so constructed as to take vertical 

 hauls showing the vertical distribution of the organisms captured, 

 the others, towing-nets taking horizontal hauls along the surface. 

 Many of the alga?, especially the coarser ones, along with attached 

 or entangled diatoms and desmids were collected by hand along 

 shore. The charas were all gathered by hand or dredge. 



