Bacteria in their Relation to Vegetable Tissue. 11 



Can bacteria penetrate the intact healthy tissue of the plant ? 

 In considering this question we may disregard, in this connection, 

 those cases where bacteria have gained access to the inner tissues by 

 means of wounds, and have been able to live there for a certain time. 

 The question as stated above is of practical importance in pathology, 

 for if micro-organisms are able to penetrate the intact tissues, this 

 will explain the way in which infectious material may be distributed 

 from plant to plant. 



The epidermal tissues of the plant are much more resistant to 

 external influences than the parenchymatous elements. This is due 

 to an outer layer of pure cutin, or to the impregnation of the cellu- 

 lose walls with cutinized layers. This resistant sheath is replaced 

 in the older plant by a thicker and more resistant corky layer. 

 These protecting tissues are not perfectly continuous over the 

 exterior of the plant, but are pierced by numerous small openings, 

 the stomata, which afford a direct communication between the sur- 

 rounding atmosphere and the inner cells of the plant. 



What is now to prevent the entrance of micro-organisms through 

 these minute openings in the outer membrane? 



As regards fungi we know that some species, such as Cystopus 

 candidus, the common white rust of Cruciferse, do gain access to 

 the inner tissues, first, by sending their germ-tubes through the 

 stomata into the intercellular spaces. As these spaces are devoid of 

 nutrient material, they must offer but poor conditions for growth 

 to any organism that is not able to extract its nutriment from the 

 living cell, either by haustoria or by penetrating the wall and, by 

 means of ferment action, obtaining access to the protoplasmic 

 materials of the cell. 



With bacteria that are not adapted for a parasitic existence in plant- 

 tissue it is not yet definitely determined whether they can enter by 

 means of these natural openings. I was unable to isolate from the 

 tissue of different plants any bacteria, although the pots and their 

 plants were watered for several days with dilute infusions of the 

 different germs. The results I obtained are not at all in harmony 

 with those of Lominsky, who found that wheat could infect itself 

 naturally in soil seeded with different species of bacteria. Not only 

 was he able to isolate from the roots of the growing plant all the 

 species which he added to the soil, but he found them also in the 



