274 BACTERIA IN RELATION TO PLANT DISEASES. 



From a liter of alkaline potato juice inoculated 8 days a clear, bacteria-free fluid was obtained by 

 passing it through a Chamberland filter. When double its volume of absolute alcohol was added a 

 copious precipitate was obtained, which was tested after further purification for its effect on cell-walls 

 of potato tubers. The walls became swollen and the typical rot appeared within 36 hours at 37 C. 

 Here again high temperatures were necessary, i. e., such as usually do not occur in the field or in 

 storage. I translate as follows: 



Experiments with enzyme injection at different temperatures showed after 3 days at 2 to 28 C. 

 no action; at 29 C. beginning of rot; at 30 to 35 C. feeble rot spots; at 36 to 38 C. strong wet 

 rot; at 40 to 45 C. again feeble decay; at 60 C. no decay. 



At 35 C. the swollen cell walls became twice their normal width in 18 hours and the cells sepa- 

 rated wholly or partly along the line of the middle lamella the third day. After 8 days the starch- 

 grains were also acted upon, resembling the skeletons obtained by exposing starch to saliva at 40 C. 

 This remainder, which does not fall apart, is believed to be amylodextrin. Corrosion from the margin 

 did not occur. The enzyme which dissolves the middle lamella is designated Xanthochlorum 

 hemicellulase. 



When thin sections of a potato tuber are put into infected potato juice and examined under the 

 microscope, the protoplasm can be seen to separate from the walls of the cell after 10 minutes, and 

 after 40 minutes it lies as a dark-brown lump dead in the middle of the cell; therefore the bacteria 

 excrete a toxin as well as an enzyme. 



According to Schuster, the action of this organism on the stems of Vicia faba is very 

 rapid even at room- temperatures; pitch-black spots appear at the place of inoculation and 

 within 24 hours the stems rot and fall over, but it is not clear to the writer whether these 

 inoculations were done on plants under bell-jars, or in the open, i. e,, under normal condi- 

 tions.* Schuster's figures 8, 9, and 10 indicate a vascular infection. The rapidity of 

 stomatal infection on leaves of Vicia faba is something hitherto unheard of, viz, penetration 

 of the stomata with brown staining and bacterial occupation of the vessels of the leaflets, 

 of the petiole, and even of the stem, within 48 hours, and would seem to indicate drenching 

 of the leaves with bacteria and exposure to other abnormal conditions, i. e., to air saturated 

 with vapor of water [see below]. The spiral vessels are the first to be attacked; the pitted 

 vessels are then occupied, the bacteria entering them through the pits; subsequently larger 

 or smaller cavities are formed in the vascular bundle. 



When cultivated from stems of Vicia faba on alkaline potato agar at 30 C., a weak 

 reddish stain appears which soon turns black on addition of paraphenylendiamin and 

 /3-naphthol (Spitzer's reaction). This red reaction is plainer in cultures to which i to 5 

 per cent tyrosin solution has been added. 



The rot on lupins was white, never black as on Vicia. The plants were injected and 

 kept moist under bell-jars. The plants in the open were never destroyed by the inoculation, 

 the growth of the bacteria soon ceased and the wounds dried out, but here pustule-like 

 intumescences were observed [see below], and these are ascribed to the action of the organism, 

 since the control plants remained free whether pricked or not (see this monograph, Vol. 

 II, fig. 27). In Physalis also the rot was white. 



EXPERIMENTS IN WASHINGTON. 



The writer repeated certain of these experiments with a green-fluorescent organism 

 brought in 1911 from the Biologisches Anstalt in Berlin by Dr. Wollenweber and said 

 to be Bad. xantkochlorum Schuster. This culture, it should be stated, did not come directly 

 from Dr. Schuster, who had then left the laboratory, but was a transfer by another assistant 

 from a stock culture of this organism. 



The organism which I have thus received and studied liquefies gelatin in the manner 

 described and rots potato tubers as described, only much more slowly at 26 C,, and not 

 at all at 37.5C., nor will it grow in culture media at that temperature. Also on Vicia faba 



Dr. Wollenweber, who was at the Biologisches Anstalt during this period, tells me they were made under bell-jars 

 in the laboratory. 



