276 



BACTERIA IN RELATION TO PLANT DISEASES. 



Several of the inoculated potato tubers exposed dry at room-temperature (26 C.) 

 showed a slight vascular infection (rot) extending in one instance a distance of 2 cm. from 

 the pricked area, but only visible close to the bundles. The check-pricked tubers remained 



sound. The experiments were made in August, i. e., on 

 I tubers recently harvested (fig. 135), and part of a lot 

 which rotted quickly when exposed to B. melanogenes. 

 Miss Nellie Brown repeated this experiment for me on 

 several potato tubers with the same result. 



Dr. Schuster's figures also call for some interpreta- 

 tion or explanation. I am inclined to think they do not 

 represent what actually took place in the tissues; by 

 this I mean that some of them are suspiciously diagram- 

 matic. Schuster's text figure No. 11, for instance, can 

 hardly represent a stomatal infection in Yicia faba. 

 Here the bacteria are represented as forming a branch- 

 ing strand which has entered through the stoma and 

 penetrated to the opposite side of the leaf in a very un- 

 usual way, i. e., by boring its way through cell- walls. 

 It has conspicuously avoided the intercellular spaces, 

 and the surrounding cells are not only unoccupied by 

 the bacteria but also uncollapsed and apparently unin- 

 jured and the leaf has retained its turgor. I am told 

 that Dr. Schuster did not make these drawings, but he 

 ought, at least, to have supervised them, since profes- 

 sional artists seldom have an eye for details of plant 

 structure. In an unusual case like this, a photomicro- 

 graph would have been more convincing. 



The subject is left in such shape that some careful 

 bacteriologist should repeat all of Schuster's experi- 

 ments, and make others; only in this way shall we finally 

 come to know what weight to give his statements. 



On a few of the many plants of Viciafaba inocu- 

 lated by me where the needle-inoculations were not far 

 apart, and one above another, the rapidly growing stems 

 cracked open with callus-formation not unlike that 

 figured by Schuster for Lupinus, but there was no evi- 

 dence of disease due to the bacteria. These stems were 

 about 15 inches high when inoculated and were 5 feet tall with numerous vigorous leaves 

 and blossoms when the photograph was made (fig. 136). 



Fig. 136/ 



LITERATURE. 



1912. 



1912. 



Schuster, Julius. Zur Kenntniss der Bak- 

 terienfaule der KartofTel. Arbeiten aus der 

 K. Biologischen Anstalt f. Land. u. Forst- 

 wirtschaft, VIII Bd., 4 Heft, pp. 452-492. 

 1 plate, 13 figs. Berlin, 1912. 



Smith, Krwin F. Isolation of pathogenic 

 potato bacteria: A question of priority. 

 Phytopathology, vol.11, p. 213, Oct. 1912. 



1913. Brown, Nellie A., and Jamieson, Clara O. 

 A bacterium [Bad. aptatum] causing a disease 

 of sugar-beet and nasturtium leaves. Jour. 

 Agric. Research, U. S. Dept. of Agric., vol. 1, 

 No. 3, Dec., 1913, with 3 pis. (one-colored), 

 pp. 189-210. That part relating to Schuster's 

 organism begins on page 209. 



*Fig. 136. Stem of Vicia faba, 2.5 months after inoculating with Schuster's Bacterium xanthochlorum, showing 

 tissue cracked open, with callus formation along the line of needle-pricks. X 1.75. 



