July 10, 1916 



Storage-Rots of Economic Avoids 



561 



INOCULATION OF XANTHOSOMA SAGITTIFOUUM 



On January 25 sixteen inoculations were made by placing bits of 

 hyphae on the cut surface and in 12 days all were sof trotted and sclerotia 

 abundantly produced. The six checks remained sound. 



The results of the inoculation experiments with S. rolfsii are given in 

 Table III. 



Table III. — Restilts of inoculation experiments with Sclerotium rolfsii 



SOFTROT 



Many tubers have been examined which were softrotted and emitted 

 a very disagreeable, repellent odor. At first the odor was supposed to 

 be produced by saprophytic bacteria following the invasion of the host 

 by some one of the organisms already discussed. From many such 

 specimens, however, after paring away most of the rotted material, 

 no fungi could be isolated. Microscopic examination of such material 

 disclosed very actively motile bacteria which were readily isolated by 

 the poured-plate method. 



This is the only disease of the four studied which occurs to some extent 

 in the field, mostly in the lower and poorly drained parts. Plate 

 LXXXIII shows a corm and leaf attached as it appeared when lifted 

 in the field. The lower part of the corm is decayed away. The organism 

 isolated from this corm was used in some of the inoculation experiments 

 which follow. The organism was also isolated from tubers and corms 

 in the storage piles and once from the dark strands running through the 

 corms. These strands sometimes appeared darker than normal, and 

 microscopic examinations indicated invasion by some organism, but 

 repeated attempts to isolate one failed until the winter of 191 5, when a 

 bacterium was isolated from a diseased strand in the center of a big corm 

 by macerating bits of the decayed tissue in a tube of sterile water and 

 pouring agar plates in the customary way. Numerous colonies later 

 developed which proved to be identical with that produced by the other 

 strains isolated from rotted tissue and to produce a rot similar to it. 

 Usually these strands can be traced to the exterior of the corm, showing 

 that the invading organism probably followed the strand. Under suit- 



