BEPORT OF THE SOCIETY 117 



disputed. In the derivatives of 7al there is a greater difference in that the lique- 

 faction is so slight as to be practically negligible. In all other characteristics, 

 however, the differences are only of minor importance. 



From the above study of the two pathogens causing the soft rot of Iris, it 

 appears to the writer that the organisms, although not identical with B. caroto- 

 vorus, do not vary sufficiently from it to become new species, therefore should be 

 considered merely as slightly different varieties of the original organism des- 

 cribed by Jones. 



Smith (9) states that B. oleraceae (Harrison), B. omnivorus (Van Hall), 

 and 5. apivorus (Wormold)are apparently identical with B. carotovorus (Jones), 

 and since the writer proved the organism causing soft rot of Iris to be a vanety 

 of B. carotovorus, it therefore appears that the organism causing the disease in 

 this country is similar to that causing the disease in Europe. 



Pathological Histology. 



The material for this study was taken from various parts of the plant, both 

 leaf and rhizome, in different stages of infection. Both naturally and artifi- 

 cially inoculated plants were used. The samples were killed and prepared in the 

 usual way for microtome sectioning. The sections were in most cases stained 

 with carbol f uchsin, but occasionally Delafield's haema toxylin was used. 



Patliological Effect on the Rhizome. 



The cells of healthy rhizome tissue are very uniform in size and shape. The 

 difference in size of the cells in respective sections may be due to the fact that 

 they are taken from plants of different varieties or from different parts of the 

 rhizome. The cells contain large numbers of starch grains, the protoplasm 

 being almost entirely hidden except for the very distinct nuclei. 



The progress of the disease in the rhizome is extremely rapid and, therefore, 

 the writer was unable to obtain good specimens of the primary effect of the 

 pathogen upon the host tissues. The cell walls gradually become broken down, 

 and the cell shape is far less definite than in the healthy tissue. The destruc- 

 tion of the middle lamellae and thus the separation of the cells from one another 

 can be seen in many places. In the primar3Mnfected tissues it can also be noted 

 that the cell contents, both starch and protoplasmic commence to disintegrate. 

 The starch grains are fewer in number than in the healthy tissues and less regu- 

 larly placed. Plasmolysis also occurs combined with a sHght enlargement of the 

 nuclei. 



As the disease progresses the cell contents gradually become more plasmo- 

 lyzed and disintegrated until they have practically disappeared. The last part 

 of the cell contents to disintegrate is the nucleus, but as the disease progresses, 

 this also becomes broken down and the whole cell contents, resemble an irre- 



