Microbiol til 



even though organic fertilizations almost invariably produce large 

 increases in the soil population. In some work (U7) in which 

 manured, untreated, and steam-sterilized soils were variously layered, 

 one above another, and then cropped to wheat, the root microflora was 

 found to be largely independent of the soil flora. Other workers 

 also have noted the independence of the root and soil floras, except- 

 ing insofar as manuring may effect growth rate and vigor of the plants. 

 Possibly the indirect effects accoiint for the finding of Hildebrand 

 and West (US) that manurial treatment affecting the incidence of 

 Ontario rot of strawberries also affected the relative incidence of 

 nutritional groups within the rhizosphere. 



That root microfloras have been found largely independent of soil 

 treatment is not surprising. Stanier (U9) has pointed out that the 

 microbial environment is a micro-environment, "hundreds or even 

 thousands or which lie concealed from the gross ecological eye in 

 any gram of soil. A single cellulose fibre provides a specialized 

 environment with its own characteristic microflora, yet may occupy a 

 volume of not more than a cubic millimeter." 



The root siirface is likewise a inicro-environment. Whether or not 

 additional micro-environments, with a wealth of microorganisms, are 

 set up in the soil by the addition of the numerous bits and pieces of 

 an organic manure is largely immaterial to the microbes in the rhizo- 



plane . 



Soil bacteriologist long have attempted to control the root surface 

 microflora by seed inoculations. Notable success has, of coiirse, been 

 achieved in the inoculation of legumes with rhizobia. Inoculations 

 with non-parasitic bacteria other than rhizobia have, for the most 

 part, been without success. This failure can be blamed neither on any 

 paucity of attempts by serious-minded workers, nor on any lack of 

 enthusiasm or sanguine statements on the part of those who have at- 

 tempted to market various miracle inoculants. Quite apart from any 

 personal profit motive, a great number of inoculation attempts have 

 been made in efforts to secure root rot control. Our previous citation 

 from Garrett (36), concerning the stillborn child qxiietly laid to rest 

 under the inscription of "Biological Control by Inoculation of the 

 Soil with Antagonistic Microorganisms," emphasizes that, in Garret's 

 opinion, most such inoculation attempts have been unsuccessful. 



There are some contrary views. Morrow and associates (50) were of the 

 opinion that either fungi or bacteria could be established on cotton 

 roots by use of proper inocula. In my opinion, they failed to demon- 

 strate that their recoveries represented more than chance occurrence 

 or perhaps a passive survival. More convincing and more sharply limited 

 data have recently been presented by Wright (5l) who has found that 

 Pythiijmi damage to mustard plant seedlings can, to some extent, be con- 

 trolled by inoculation of the seeds with some common soil saprophytes. 



