W. F. Bewley and W. Buddin 19 



badly contaminated with disease organisms. Ponds full of algae and 

 weeds are suitable breeding places for fungi and bacteria. Shallow wells 

 receive surface drainage from the neighbouring land and are liable to 

 be contaminated, especially if heaps of decaying plants are deposited in 

 their vicinity. Deep artesian wells are the purest and safest. Care 

 should be taken to cover all wells and tanks to prevent contamination 

 with debris that otherwise might gain entrance. 



Summary. 



1. Nursery waters in the Lea Valley have been examined and some 

 shown to be an important source of disease. 



2. Contaminated waters may be purified by filtering, boiling and by 

 addition of certain chemicals. 



REFERENCES. 



(1) Cook, M. T. (1911). Delaware Agr. Exp. 8ta. Bid. 91. 



(2) Clinton, G. P. (1909-1910). Conn. Agr. Exp. Ski. Rep. 



(3) Dastur, J. F. (1913). Mem. Dept. Agri. India, Bot. Ser., v. No. 4. 



(4) Paine, S. G. and Bewley, W. F. (1919). Ann. App. Biol, vi, Nos. 2 and 3. 



(5) Pethybridge, G. H. and Lafferty, H. A. (1919). Proc. Roy. Dublin Soc. xv 



(N.S.), No. 35. 



(6) Waksman, S. a. (1917). Soil Sci., in. No. G. 



{Received February 8th, 1921.) 



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