80 Fresh-water Biology 



Study 15 

 THE ''BLANKET ALGAE" ASSOCIATION 



This is a study of some of the minute animals and plants that live in floating masses 

 of green algae in still water. If pailsful of such material be gathered (as by lifting it gently 

 from the water with a dip net), brought into the laboratory and distributed in white- 

 bottomed dishes for individual student's use (a handful in each dish), and left standing 

 undisturbed for a few minutes, there will be good collecting with a dropping tube about 

 the edges of the dish. There will be algae in variety, and many kinds of minute animals. 

 A moment's inspection of the latter will show that they differ in size, color, form, speed and 

 manner of swimming. 



This is a study of the forms that are large enough to be discovered with the unaided 

 eye, and small enough to be picked up with an ordinary dropping tube. They are to be 

 placed on slides for examination with a microscope. 



Work Program: 



1. A laboratory examination of samples of the floating "blanket algae" from some 



pond or pool or sheltered bay. 



2. Reading in the text about the several groups of which representatives are found. 



Emilie L. Piatt's Population of the Blanket Algae of Pools (Amer. Nat. 49: 752) 

 may be consulted with profit. 



For Record include: 



1. A brief statement of the nature and source of the materials examined. 



2. An annotated and illustrated list of the organisms found with notes on all of them 



and with simple outline sketches of representatives of the groups named below: 



I. Plants — with notes on size, color, growth habit, etc. 



Diatoms. Desmids. Blue greens. 

 Filamentous green algae. Other green algae. 



II. Animals — with notes on size, color, stages or ages found, habits of locomotion, 



of feeding, etc. 



Insects (very young stages of such as mayflies, dragonflies, damselflies, bugs, 

 caddisflies, midges,* mosquitoes and other two- winged flies, and beetles. 



Crustaceans (scuds, cladocerans, copepods and ostracods. 



Molluscs (snails). 



The larger rotifers. 



Other invertebrates especially water mites, hydras, young leeches, and 

 bristle worms). 



* Recognizable in swimming by their figure-of-8 loopings. 



