DISEASES AND PESTS 61 



by isolation and identification of the germ from 

 diseased trees, and by the inoculation of previously 

 healthy trees with pure cultures of this bacterium, even 

 by cultures of animal origin, and the consequent 

 production of the disease. A few of Johnston's ex- 

 periments seem to indicate that other similar bacteria 

 may also produce bud rot ; but it is certain that in 

 the great majority of cases this organism is present 

 and pathogenic. This fact is completely confirmed by 

 Rorer, who has found, moreover, that, whether or not 

 infection is sometimes or usually at points already 

 injured mechanically or by fungi, a culture of Bacillus 

 coli poured into the crown of an apparently perfectly 

 sound tree is able to produce the disease. 



Neither Johnston nor Rorer believes that Diplodia 

 has anything to do with the bud rot. In this con- 

 nection Rorer says : 



Although Stockdale has attributed the root disease to a 

 species of Diplodia, there is no ground for this assumption. In 

 fact, work which has been carried on here for the past two years 

 points to the conclusion that physiological conditions, rather 

 than any specific organic parasite, are responsible for the trouble. 



I take the liberty of saying that Bancroft, whose 

 especially thorough study of Diplodia in the Federated 

 Malay States has already been mentioned, expresses the 

 decided opinion that this fungus is not an active parasite, 

 and is accordingly very unlikely to be a precursor of 

 bud rot. 



In spite of the joint judgment of these latest writers, 

 I have thought it worth while to give the conclusions 

 of Fredholm and Stockdale with considerable fulness, 

 not merely for the sake of completeness, but also because 

 their work in itself seems at a distance to be entitled 

 to some respect. It is difficult to believe, even from 

 Johnston's own account of the various ways in which 

 the symptoms of bud rot develop, that a single organism 

 is always entirely responsible. When the first symptom 

 is the fall of the older leaves, one who holds to the 



