12 BACTERIA IN RELATION TO PLANT DISEASES. 



infection might succeed, it would be necessary to suppose bacteria mobile, capable of crawling into 

 the intercellular spaces, something quite improbable (ce que est assez peu vraisemblable), or else 

 filamentous forms with continuous development, in the manner of the mycelial filaments of fungi. 

 As to short non-motile bacteria, they would have to traverse the cell membranes. * * * Now 

 I have determined that the cellulose, even of the most tender varieties, resists perfectly, exposed 

 to the air, a great number of kinds of common bacteria. The solvent action of Bacillus amylobacter 

 takes place only in the absence of oxygen. Nevertheless, according to Vignal, the Bacillus mesen- 

 teric us vulgatus secretes a zymase which digests the most tender celluloses. I have made the same 

 observation in case of a Bacillus subtil is, which, when developed in mycoderma on the surface of 

 a liquid, separated the cells of a bit of potato situated in the depths of the same liquid. In con- 

 clusion, if the penetration of the cell-membranes of plants is not a general property of the bacteria 

 it does occur and may perhaps be developed in a particularly favorable medium. 



This condition is nevertheless not sufficient to enable the bacteria which are outside to estab- 

 lish themselves in the tissues of plants. It is necessary also to take account of the resistance peculiar 

 to living cells, a resistance the mechanism of which is still entirely enigmatic. Among animals, the 

 pathogenic bacteria overcome this difficulty by the production of substances more or less toxic, 

 rapidly diffused through the entire organism by way of the blood stream. The higher plants have 

 the advantage of being much more resistant to the movement of the microbes and of their secretions 

 through their tissues. Consequently there exist few bacterial diseases among plants, while in the 

 animal kingdom there are a great many of them. 



Kirchner (1890) mentions two bacteria, Bad. termo Ehr. which has been said to take 

 part in the destruction of cells in the interior of sorghum-stems, and Clostridium butyricum 

 Prazm., which "causes the wet-rot and dry-rot of potato-tubers and the rot of onions; 

 also on the roots of apple trees, pear trees, plum trees, and cherry trees." 



Scribner (1890), says in his preface: "We are told that bacteria cause pear-blight and 

 some other plant diseases," but does not mention the subject in the body of the text. 



In his Diseases of Plants, published in 1890, Marshall Ward does not mention bac- 

 teria as one of the causes, although he also has a chapter on "the potato disease." 



Comes (1891), like Sorauer, admits without reserve the existence of such a class of 

 diseases and treats the subject constructively, in a space of 38 pages. The organisms con- 

 sidered are Micrococcus amylovorus , Bad. gummis, Bad. zeae, Streptococcus bombycis, Bacillus 

 sorghi, B, amylobacter, B. hyacinthi, B. caulivorus, B. vuillemini, B. oleae, B. ampelopsorae, 

 and B. radicicola. 



Ludwig (1892) also recognizes the existence of bacterial diseases of plants and devotes 

 about 8 pages to the subject, but this does not include any original work. 



Loverdo (1892) recognizes the existence of bacterial diseases and devotes a number of 

 pages to an account of the sorghum blight attributed to Bacillus sorghi. 



By far the best paper of its time (1892) is that written by Migula for the Middle Java 

 Experiment Station. Without personal knowledge of bacterial diseases, but with a knowl- 

 edge of most of the literature, and a logical mind, Dr. Migula applies the ordinary rules 

 of pathological inquiry to the question of the existence of bacterial diseases of plants, and 

 conies to the conclusion that five only out of about twenty which are mentioned deserve 

 to be considered as clearly established. These are pear-blight or apple-blight, sorghum- 

 blight, Burrill's bacterial disease of maize, Heinz's rot of hyacinth, and Kramer's wet-rot 

 of the potato. 



Russell, who published the same year as Migula, also admits the existence of bacterial 

 diseases of plants, but like Migula, his observations were based mainly on the work of others. 

 In tables at the end of his paper, he mentions 13 diseases as of established bacterial origin 

 and 9 as "probably of bacterial origin," i. e. 22 in all. The following were included in his 

 first class: pear-blight, Burrill's sorghum-blight, Burrill's corn-blight, Wakker's yellows of 

 hyacinth, Heinz's hyacinth rot, tuberculosis of olive, and of Aleppo pine, blight of oats, 

 Arthur's carnation blight, Bolley's potato scab, Burrill's wet-rot of potato, Kramer's wet-rot 

 of potato, sugar-beet disease of Arthur and Golden. In the second class were geranium- 

 blight of Prillieux and Delacroix, Halsted's cucumber and tomato-blight, Halsted's root-rot 



