INJURIES INDUCED BY PLANTS 37 



BACTERIA, OR SCHIZOMYCETES 



It was not till a few years ago that bacteria were recognized 

 as plant-infesting parasites, and only in extremely isolated cases 

 has it been placed beyond doubt that these low organisms are 

 the primary cause of disease in plants.* 



Whereas the processes of decay, and most of the infectious 

 diseases of man and animals, may be traced to bacteria, the plant- 

 organism is protected against them by the peculiarity of its 

 structure, and especially by the absence of circulatory channels 

 for conducting the nutrient fluids which could serve to distribute 

 any lowly organisms which might happen to be present in the 

 food. It is only by means of the vessels and intercellular spaces 

 that they can distribute themselves in any great numbers in the 

 body of the plant, for in other cases they have to pass through 

 the cellulose or woody cell-walls, which offer great resistance to 

 their attack. 



In addition to this, the vegetable juices, most of which show 

 an acid reaction, are unfavourable to their growth. As a matter 

 of fact, bacteria have hitherto been found only in the tissues 

 of plants whose cells are parenchymatous in character and 

 possessed of very delicate walls, as, for instance, bulbs and 

 tubers. Sorauer l applies the collective name bacteriosis 

 to diseases due to bacteria. These diseases are characterised 

 by the fact that the succulent parts of the infested plant are 

 converted into a slimy glutinous pulp, which emits a most 

 repulsive stench. Owing to the action of those bacteria 

 which have advanced more rapidly along, and spread out from, 

 the vessels, the delicate walls of the cells are dissolved, being 

 employed, along with their protoplasmic and other contents, in 

 nourishing and fostering the bacteria, whereas the starch is often 

 left intact. 



The yellow " bacteriosis " of the bulbs of hyacinths (Bacterium 

 Hyacinth?) is a common disease. Here the yellow slimy masses 



1 Sorauer, Handbuch. 2nd Edition. Pp. 74 112. 



* [Russell has recently put together the literature on this subject in a 

 dissertation to the John Hopkins University, Baltimore, 1892. ED.] 



