610 MINNESOTA BOTANICAL STUDIES. 



Method of collection. The method of collection is practically 

 the one suggested by Dr. Smith Ely Jelliffe * and is as follows : 

 A piece of absorbent cotton four or five inches square and one 

 inch thick is attached by means of a twelve-inch square of un- 

 bleached muslin to the water faucet. The water is then turned 

 on sufficiently to insure a constant stream and is allowed to run 

 from ten to twelve hours, after which the cotton is removed. 

 The cotton, which is usually quite brown from the organisms, 

 is divided into pieces and rubbed and rinsed in five beakers each 

 containing 200 c.c. of water. The water is then poured into 

 one vessel and allowed to settle, after which the deposit is put 

 into a glass containing 25 c.c. A few drops of this is trans- 

 ferred to a slide by means of a pipette and examined microscop- 

 ically. At least ten mounts from each week's collection of ma- 

 terial was examined in this wa}^. The rest was then preserved 

 in 2 per cent, formaline for future reference. 



For the records, Dr. Jelliffe's method of computation was 

 adopted. In computing the numbers the following schedule 

 was used : 



Abundant, 25 + in one c.c. of water. 



Common, 10-25 in one c.c. of water. 



Few, 5-10 in one c.c. of water. 



Scarce, 1-5 in one c.c. of water. 



Present, Less than five in one c.c. of water. 



Since November, 1899, weekly collections have been made of 

 the plant life in the St. Paul water supply and the organisms 

 identified (as far as possible) and their number computed. 



The vegetable organisms found were all algas if we except 

 the pollen grains and Fungi spores that appeared occasionally. 

 The Algse found were as follows : 



1. Diatomacece, 13 varieties. 



2. Cyanophycece, n varieties. 



3. Cklor<rphyce<&) 32 varieties. 



4. PeridinicR, 2 varieties. 



Of these some forms of Diatoms were present almost con- 

 stantly, especially Melosira, Stephanodiscns, two varieties of 



* Jelliffe, S. E. A preliminary report upon the microscopical organisms found 

 in the Brooklyn water supply. Brooklyn Med. Journ. 7 : 595. O. 1893. 



