of the T (i r iii ( i (I'>rassica uapus). 449 



the elimination of bacteria, was desired was effected through ordinary 

 filter paper. The quantity of the precipitate being small, the portion 

 of the paper upon which it was deposited was cut out and digested 

 with water. But in order to avoid any possible action of the enzyme 

 upon the paper, kieselguhr was subsequently invariably employed, a 

 few pieces of glass at the base of the funnel covered with a little 

 asbestos serving to prevent the kieselguhr from passing through, 

 the necessary pressure to ensure nitration being derived from an air- 

 pump. 



The filtered extract from the rotten turnip also contains a diastasic 

 ferment. Two test-tubes, each containing 5 c.c. of the dissolved 

 ferment, were diluted with 5 c.c. of a 1 per cent, starch emulsion, one of 

 the test-tubes having previously been boiled. After twenty-four hours 

 the test-tube with the unboiled ferment showed no starch reaction on 

 the addition of iodine ; but the boiled tube at once gave the character- 

 istic blue. 



Similar diastasic enzymes are excreted by several other bacteria 

 (Lafar). 



It will be convenient here to say that, adopting Migula's classifica- 

 tion, I have ventured to name the bacterium I am describing 

 Pseudommas destructans, though the description will be given later. 



It has been established that P. destructans, both when living in a 

 nutrient solution and on a living turnip, excretes an enzyme which 

 has the power of dissolving the middle lamella and of causing the 

 softening and swelling of the cell-wall. 



As a further result of the bacterial action, as already described, the 

 protoplasm of the cells is- found to have contracted, become brown, 

 and separated from the cell-wall, showing evidence of the action of a 

 toxin secreted by the bacterium. The same effect was produced in 

 living turnip cells when treated with the boiled pressed juice of a 

 turnip, which had become rotten through the influence of a pure 

 culture of P. destructans. The pressed juice was filtered and about 

 10 c.c. drawn into test-tubes, which were then plugged and sterilised 

 by discontinuous boiling. Sections cut by a razor, sterilised by boiling, 

 from blocks of sterile, living turnip (p. 444) were quickly transferred 

 to the boiled juice after it had cooled; at the same time similar 

 sections were immersed in test-tubes containing the same quantity 

 of sterile water. After twelve hours a very marked contrast was 

 observable between these sections. In those immersed in the sterile 

 water the cells presented the normal appearance, with the protoplasm 

 pressed close to the cell-wall, while in those in the boiled pressed 

 juice the protoplasm was dead, had assumed a brown tint, and 

 contracted away from the cell-wall. A toxin, therefore, which is 

 not destroyed by boiling is secreted by P. destructans. 



In his paper " Ueber einige Sclerotinien und Sclerotien-Krank- 



VOT.. LXVII. 2 K 



