50 



BACTERIA IN RELATION TO PLANT DISEASES. 



filtrate placed on a slice of potato killed a large portion of it within 24 hours. When a voluminous 

 precipitate, obtained by adding (2:1) alcohol, was dried in the thermostat, pulverized, and placed 

 on potato, it was very destructive. After 2 hours at 37° C. much of the tissue was attacked and 

 killed. Heating to the boiling point destroyed the toxic effect of the filtrate. At 37° it was very 

 active, at 30° weak, and at 23° ineffective. Neutralization with hydrochloric acid did not destroy 

 its toxic qualities. The presence of this toxic substance was also demonstrated in the artificial 

 cultures. 



Another experiment to demonstrate the secretion of a toxin was as follows: A small piece of 

 malt-agar, on which a streak culture had made a luxuriant growth, was cut out with a sterile knife, 

 placed on a freshly cut slice of potato, and kept in the thermostat at 37°. Within one day the effect 

 of the toxin was visible, for just below the strip of agar the tissue was dead and formed a soft mass. 

 Streak cultiu-es on several other sorts of nutrient agar all grew luxuriantly, but were different in 

 their toxic effects. Strips of agar from cultures on bouillon-agar acted as destructively as those 

 from malt-agar, but the action of those from saccharose-pepton-agar, and saccharose-asparagin- 

 agar was weak, while strips from cultures on saccharose-potassium-nitrate-agar, and saccharose- 

 ammonium-sulphate-agar produced no toxic effects. Most of the paper is devoted to B. subtilis. 

 Bacillus vulgatus required for parasitic activity a higher temperature than B. subtilis, attack- 

 ing occasionally a few plants at 37°, but many at 42° C. Shiny spots were formed which were at 

 times covered with a folded bacterial membrane. On potato at 37°C. there appeared occasionally 

 among the spots due to B. subtilis small, round, viscid, slimy spheres, which decayed small portions 

 of the tissue. These spots contained B. vulgatus almost exclusively. On agar cultures from these 

 spots the bacteria showed some differences, but only minor ones, probably indicating sub-species. 



B. vulgatus lost and regained its virulence in the same manner as B. subtilis. Decay progressed 

 similarly, only the color and odor differed somewhat. A strong toxin was produced in cultures on 

 all the media used. 



The fact that these bacteria become parasitic only at high temperatures makes it improbable 

 that they are ever responsible for damage in this climate (Holland), but it is not impossible that in 

 warmer climates they might be dangerous agents of decay. 



In 1903 Muth published an account of his experiments on the variations in seed-ger- 

 mination (made on 32 species), in which he states that his results lead him to disagree with 

 Laurent, Lepoutre, and van Hall regarding the adaptability of Bacillus coli, etc., to a 

 parasitic life. The experiment which led him to this conclusion is given below. 



He tested the effect of inoculating before germination, carefidly washed seeds with pure cul- 

 tures of fungi (Aspergillus, Penicillium, Mucor, Botrytis, and Cladosporium),a.ndoi bacteria (B. coli, 

 B. mycoides, B. fluorescens liquefaciens, B. asterosporus, and a bacillus out of truffle conserves). 



The fungi gave very positive results; almost all the seeds were attacked. The results with 

 bacteria on the other hand were almost completely negative. The infections produced were doubt- 

 ful ones, and so few in proportion to the whole number inoculated that he considered ftirther experi- 

 ments necessary to determine whether there was any action whatever. 



LITERATURE. 



1879. Rbinkb, J. UND Berthold, G. Die Zersetzung 

 der Kartoffel durch Pilze. Mit neun (9) 

 lithographirten Tafeln. Berlin, 1879, Verlag 

 von Wiegandt, Hempel & Parey (Paul Parey), 

 pp. 100. Untersuchungen aus dem Bot. 

 Laboratorium der Univ. Gottingen Herausge- 

 gebenen von Dr. J. Reinke, i. 



1899. Laurent, EmilE. Recherches experimentales 



sur les Maladies des Plantes. Annales de 

 rinstitut Pasteur, No. i, Jan., 1899, pages i 

 to 48. 



1900. Jensen, Hjalmar. Versuche tiber Bakterien- 



krankheiten bei Kartoffeln. Centralb. f. 

 Bakt., .i Abt.,Bd. vi. No. 20, Jena, Oct., 1900, 

 pp. 641-648. 



1902. Hall, C. J. J. van. Bacillus subtilis (Ehr.) 

 Cohn und B. vulgatus (Fliigge) Mig. als 

 Pflanzenparasiten. Centralb. f. Bakt., 2 Abt., 

 Bd. IX, 1902, pp. 642-652. 



1902. Lepoutre, L. Recherches sur la production 

 experimentale de races parasites des plantes 

 chez les bact^ries banales. C. R. des s€. de 

 I'Acad. des Sci. Paris, 1902, T. cxxxiv, pp. 

 927 to 929. 



1902. Lepoutre, L. Recherche sur la transformation 



expWmentale de bact&-ies banales en races 

 parasites des plantes. Ann. de I'lnst. Pasteur, 

 Paris, 1902, Tome xvi, pp. 304-312. 



1903. Muth, Franz. Ueber die Schwankungen bei 



Keimkraftpriifimgen der Samen imd ihre 

 Ursachen. Jahresber. der Vereinig. d. Ver- 

 treten d. angew. Botan., 1903, pp. 80-87. 



