THE POPULATION OF THE " BLANKET- ALGM" 

 OP FRESHWATER POOLS 1 



EMILIE LOUISE PLATT 

 Cornell University 



This is a study of the community of life that is bound 

 up with the floating masses of filamentous algae, popularly 

 known as " blanket-algae. " An acquaintance with this 

 population is worth cultivating for the sake of the variety, 

 beauty and interesting peculiarities of the plants and ani- 

 mals found in this unique habitat. It may be of utili- 

 tarian value as well, for there exists a relation between 

 plankton production, algal growth and fish culture. Fur- 

 thermore, it may be a help to students and to teachers of 

 biology when they are in search of certain laboratory ma- 

 terials, which in these algae masses flourish. 



Method of Collecting.— A fine silk hand net of No. 12 

 bolting cloth was used to lift the algae from the surface of 

 the water. The largest collection covered about 2,800 

 sq. cm. ; the smallest about 10 sq. cm., but most of them 

 were from 200 sq. cm. to 800 sq. cm. in area. Doubtless, 

 many active and comparatively large foraging animals, 

 such as small fishes or adult insects, escaped while the 

 net was surrounding and enveloping the mass. Probably 

 comparatively few of the smaller forms were lost through 

 the fine silk mesh of the net. The volume of the mass 

 was then computed in cubic centimeters. As the mass 

 sometimes lay in thin layers and sometimes in thicker 

 masses, the proportion of volume to surface was seldom 

 the same. About 200 cu. cm. was the average. The com- 

 ponents of the "blanket" were determined and all forms, 

 plant and animal, were listed and their size and relative 

 abundance noted. The collections were made during the 

 fall and early winter of 1912 and the spring and early 

 summer of 1913. 



Location and Character of the Pools.— The pools are 

 all located in the vicinity of Cornell University campus at 



i This study was carried on in the limnological laboratory of the depart- 

 ment of entomology of Cornell University under the direction of Professor 

 James G. Needham. 



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