Bacteria in their Relation to Vegetable Tissue. 15 



bedded in the protoplasm of the cell. In this case the cell mem- 

 branes were seen to be actually eroded by the bacillus. 



A similar condition is found with B. olese-tuberculosis in the 

 olive, and B. Veuillemini in the tumors of Pinus halapensis, where 

 actual destruction of cell walls is accomplished under the influence 

 of the germ. It is not at all improbable that those species which 

 are adapted to a parasitic existence in the plant organism may not 

 possess an eroding or fermentative ability, which would enable them 

 to break down the resistant cell walls which impede their spread. 



But how do we find it with those forms which are not so 

 thoroughly adapted to this kind of life ? It is much more difficult 

 to determine the distribution in these cases than it is where the germ 

 is able to grow luxuriantly. With the results which were obtained 

 from the inoculation of those micro-organisms that are incapable of 

 producing a genuine infection in plant-tissues, it has been shown in 

 several cases that there was a distinct tendency to spread throughout 

 the plant to a certain extent. These bacteria, which were deter- 

 mined at greater or lesser distances from the inoculation point, 

 were also definitely located in the interior of the cells. This condi- 

 tion was best seen with cultures of B. acidi lactici, but was also 

 recognized with B. luteus, B. pyocyaneus, and B. fluorescens. As 

 has already been said, we cannot explain their presence unless they 

 are able to pass through the cell walls. No openings of any kind 

 could be determined, and the only remaining possibility that sug- 

 gests itself is that they have the power, by means of a ferment 

 excreted, to work their way from cell to cell without causing a 

 permanent rupture. This we know to be the case with certain 

 Ustilaginese. They can penetrate the cell wall, which, after the 

 passage of the hypha, again closes, so that no opening is apparent. 

 With as small a structure as a bacillus this process is also con- 

 ceivable. This explanation, however, does not rest upon experi- 

 mental proof and is only suggested as a possible hypothesis. 



RESISTANCE AND IMMUNITY OF PLANTS TOWARD BACTERIA. 



The general exemption of plants from bacterial attack, which was 

 referred to in the introduction under the expression "Immunity/' 

 reveals, upon a closer consideration of the question, a series of 



