64 Pflanzenkrankheiten. 



Fichte für Stockfäule {Trantetes radiciperda). Jedenfalls ist die ganze 

 Arbeit sehr der Beachtung wert, und die daraus sich ergebenden 

 Folgerungen sind in Zukunft bei dem Studium pilzparisitärer Krank- 

 heiten wohl zu berücksichtigen. Neger (Tharandt). 



Pottep, M. C, On a method of Checking Parasitic Diseases 

 in Plants. (The Journal of iVgricultural Science III. Dec. 1908. 

 p. 102-107.) 



The author seeks to turn to useful account the admitted phj^- 

 siological fact that the waste products of metabolism of an organism, 

 when permitted to accumulate beyond a certain stage, have a ten- 

 dency ihimical to the existence of the organism itself, producing 

 results which finaly prove fatal. His experiments in this direction, 

 conducted with the parasites Pseudomonas destructans and Penicü- 

 liiitn üalicum, are recorded in the present paper. 



In the "White Rot" of Turnip caused b}^ Pseudomonas destructans, 

 a cellulose-dissolving enzyme (cytase), and a toxin fatal to the pro- 

 toplasm of the host-cell are produced. The cytase, as the author has 

 previously demonstrated is destroyed when submitted to a tempera- 

 ture of 100° C. but the substance toxic to the living plant-cell retains 

 this special property after boiling. By means of special treatment of 

 pure cultures of the bacterium a concentrated Solution of the sub- 

 stance toxic to the host-cells was obtained. This Solution was finally 

 heated which rendered it sterile and at the same time destroyed 

 the enzymes. Since the toxic Substance was possibly a waste product 

 of the bacterial metabolism, the Solution was tested as to its effect 

 on the life of the bacterium itself. Tubes of the Solution inoculated 

 with P. destructajis were found to produce no development. Freshly 

 inoculated Turnips in which the parasite was growing rigourously 

 were next employed', a portion of the toxic Solution being applied to 

 the inoculated cavity. The effect of the application was soon apparent 

 in the discoloration of the host cells. Decay also was arrested and 

 bacterial action ceased. In some cases a second or third application 

 of the Solution was necessary but in every instance it was found 

 possible to check an}^ further action of the bacteria. In the control 

 cultures the disease ran its normal course. 



The toxic Solution was thus found to contain properties undoub- 

 tedly toxic to P. destructans. At the same time it exercised a very 

 injurious influence upon the healthy cells of the Turnip, the proto- 

 plasm of those bordering on the affected tissue quickly becoming 

 brown and dead. This influence however extended only to a limited 

 area; and as the bacteria were killed the continued production of 

 the cytase became impossible and the wound was able to heal over. 



Similar experiments were performed with Penicülium üalicum 

 a fungus causing disease of orange fruits. A concentrated Solution 

 was obtained from orange juice charged with the waste products of 

 metabolism of the fungus. This when sterilized was found capable 

 of preventing the extension of the decay in oranges attacked by 

 PeniciUium. 



The results give strong support to the theory that the waste 

 products of metabolism after the elimination of the enzymes may 

 be used as a means of preventing the ravages of a parasite; and 

 the practical application of this principle appears to be worthj^ of 

 further investigation. A. D. Cotton. 



