lai 



destroyed and the cavities formed lead me to think that this substance 

 is secreted only in extremely small quantities. The results of srrowth 

 on different yegetable culture media point to the same conclusion. 

 No softening of the cell walls was observed in any of the following 

 substrata: Potato, sweet potato, sugar beet, coconut. A softening 

 of the middle lamella of carrot, turnip, and radish cylinders, was noted 

 in old cultures.^ 



A few observations were made on the related organisms. Potato, 

 coconut, rutabaga, yellow globe turnip, and radish cjdinders were 

 not softened by P)i. steiaartL Ps. cairvpedrin softened cylinders of 

 potato, rutabaga, and yellow globe turnip. 



The behavior of !*><. cam,pei<trh in the interior of various host plants, 

 in the absence of any other organism, indicates that a cytase must be 

 present, i. e. , closed cavities are formed. During the formation of these 

 cavities, which are fully occupied b}^ the bacteria, the parenchyma cells 

 are first separated from each other by a multiplication of the organism 

 in the intercellular spaces, the walls of the cells are then crushed 

 together b}' the continued multiplication of the bacteria, and become 

 more and more indistinct, until they finally disappear altogether. 



In properly fixed, paraffin-embedded material, cut in serial section, 

 all stages of the solution of the cells and the formation of these bac- 

 terial cavities may be readily observed,. especially in the easily sec- 

 tioned cabbage and turnip occupied b}^ Px. cainjjedri.s. The organisms 

 find their way into the parenchyma from the vessels, which are first 

 occupied in ways alread}^ described by the writer elsewhere. That the 

 destruction of the cell walls can be due to nothing but this organism, 

 in the disease under consideration, is shown clearly as follows: (1) 

 Because these are closed cavities, i. e., not in open connection with 

 the surface of the plant, except at long distances from the place of 

 occurrence; (2) because these cavities occur as freely in the interior 

 of plants that have become diseased from the writer's pure-culture 

 inoculations as they do in those which have become diseased naturally 

 in the fields; (3) because the microscope shows the cavities to be filled 

 exclusively by bacteria; (4) because cultures made from the interior 

 of such inoculated and diseased plants have shown 1\. canipestris to 

 be the oidy organism present; (5) because all stages in the destruction 

 of the cells and in the formation of these cavities can l)e followed in 

 serial sections, so fixed and otherwise prepared that the relation of the 

 bacteria to the various parts of the host plant is the same as iji the 

 living plant. 



/'!s. pha.'^eijli also forms cavities in the interior of the host plants. 

 Concerning Ph. uteiom'tl 1 am in doubt. 



' Sinc(> this was written, and ti)o lato to doterinine ex)>erinit'ntally, it lias occnncil 

 to inc, as till- result of readini,' I'ottcr's paiu-rs, tiiat pussil)!}' tliis solvent artinn on 

 the middle lamella is dne to the formation of anil ammonium oxalate. It cannot be 

 (hie to oxalic acid as such since this has no solvent action on turnip tissues. 



