14 Fungus Flora of Water Siqjplies 



of infection. The enumeration of the various members constituting 

 the microscopic population of the water samples are necessarily incom- 

 plete, for whilst it is possible readily to distinguish some members, 

 others such as Phytophthora cryptogea or Colletolrichum oligochaetum are 

 identifiable in mixed culture only with difficulty. Owing to the uncer- 

 tainty in determining the latter it has been omitted from the table. The 

 identification of Bacillus lathyriii), causative of "stripe" of tomatoes, is 

 a lengthy process, but in six samples this w^as attempted and the bacillus 

 found in three. With present technique, quantitative results do not 

 seem possible and consequently in comparing the fungal populations 

 of the various samples, the number of different species of parasites 

 found has been taken as an indication of the purity of the water. 



The results given in Table I clearly show that the extent of fungoid 

 contamination of the waters varies with the source from which they are 

 drawn. The purest waters are those from the Water Company (Metro- 

 politan Water Board) and deep artesian wells; there being an average 

 of 1*25 to 1'50 pathogens per sample. It is possible too that the fungi 

 found in these waters may be nozzle contaminations rather than actual 

 contaminations of the water supply. Water which had passed through 

 an uncovered tank was more contaminated than that from a covered 

 one. There is evidence that the former collects fungus spores and becomes 

 a source of contamination to the water passing through. Samples from 

 wells into which the surface drainage can readily pass yield a large num- 

 ber of species. Deep wells of this kind w^ere only slightly less contami- 

 nated than shallow wells, but shallow wells placed some distance aw^ay 

 from the glasshouses w^ere generally purer than those surrounded by 

 houses. Again, those wells, whose waters contained a large amount of 

 decaying organic matter, were richer in fungi than those whose waters 

 were clearer. Water from brooks and ponds was also highly contami- 

 nated, but a sUght reduction in the number of fungus species resulted 

 from thoroughly clearing away the vegetation. It will readily be seen 

 that the Water Company's supply and water drawn from deep artesian 

 wells are comparatively free from fungoid contaminations, while water 

 from wells polluted by surface drainage, as well as brooks and ponds, 

 may be a very serious source of infection. The various species of Phyto- 

 phthora appeared in these latter sources. 



Isolations. 



Representative isolations of the various pathogens were made, 

 grown in pure culture and tested for pathogenicity. To ascertain the 



