SUMMARY: Coli‐aerogenes bacteria were seldom found on the foliage of a wide variety of garden plants, trees and shrubs, and field plants, including pasture, except where there was a possibility of contamination by insects, animals or dust. They were present in only a few instances on the flowering heads of hay plants (wind pollinated) but on almost all the flowers of garden plants (insect pollinated). Although cereal crops are wind pollinated, coli‐aerogenes organisms were found on about one‐third of the grains examined. The question of their origin on grain is discussed. In a series of paired samples of soil and of the foliage of the covering vegetation, coli‐aerogenes organisms were present in most of the soil samples, but were absent from the foliage except where animal contamination was possible, as in the case of grazed pasture. With foliage samples unlikely to have been contaminated by animals, most of the coli‐aerogenes organisms isolated were A. cloacae, but with grazed pasture E. coli predominated, indicating contamination by grazing animals. The coli‐aerogenes floras of garden flowers and cereal grains corresponded closely, consisting in each case largely of A. cloacae.