42 THE FUNGI WHICH CAUSE PLANT DISEASE 



to decay of roots of carrot, parsnip, tumip, radish, salsify, of 

 onion bulbs, hyacinth corms, cabbage heads, celery stalks and 

 fruits of tomato, pepper and egg plant. Jones found no decay pro- 

 duced in young carrot or parsnip plants, fruits of orange, banana, 

 apple, pear, cauliflower head,* Irish potato tuber, beet root or 



tomato stems. ^"^ Infection 

 did not occur unless the 

 epidermis was broken. The 

 rotten mass was always 

 soft, wet, and exuded a 

 liquid clouded with bac- 

 teria. 



/ \ I V^ Jones ^'^ in 1909 made an 



extensive study of the cyto- 



Fio. 28. — ^B. carotovonis. After Jones. .... j. .i- 



litic enzyme of this germ. 

 This enzyme was separated by heat, filtration, formalin, phenol, 

 thymol, chloroform, diffusion, alcohol, and its conditions of pro- 

 duction and action investigated. Heating the enzyme to 60° in- 

 hibited its activity to a marked degree; higher than 63° inhibited 

 it entirely; chloroform, th3Tnol and phenol did not retard its ac- 

 tion. No loss was suffered through alcoholic precipitation and 

 resolution. The dried enzyme remained active for fully two 

 years. Its effect was greatest at 42°, less at 32° and 48°. No 

 diastatic action was observable. 



In 1909 Harding and Morse,'' from an extended study of some 

 12,000 cultures of non-chromogenic, liquefying soft>-rot bacilli 

 of some forty-three pathogenic strains (including B. carotovorus, 

 B. oleraceae, B. omnivorus, B. aroidese and what Potter regarded 

 as Pseudomonas destructans), from six different vegetables, con- 

 clude that unless later studies of the pathogenicity of these cul- 

 tures shall offer a basis for subdividing them, there is no apparent 

 reason why they should not all be considered as somewhat variant 

 members of a single botanical species. 



This conception would lead to the abandonment of the supposed 

 species mentioned above and the recognition of all of them under 

 their oldest described form, B. carotovorus Jones, which in our 



'Harding and Stewart later showed that it is capable of rotting cauli- 

 flower. 



