554 Journal of Agricultural Research vol. vi, No. i S 



tubers were kept under observation until February 17, and none showed 

 any evidence of decay. The checks, two in number, under similar con- 

 ditions but not inoculated, remained healthy. This and subsequent 

 experiments showed that better results could be obtained by merely 

 exposing the inoculated tubers to the surroundings of the laboratory 

 room. The use of moist chambers, therefore, was abandoned, with the 

 exception of an occasional trial experiment to be noted later. Disin- 

 fection likewise was no longer practiced, since the tubers were immedi- 

 ately exposed to reinfection from the air of the room. Although the rot 

 caused by D. tubericola is very easily recognized and characteristic when 

 once known, cultures were made from nearly all the decayed tubers, in 

 order to be sure the rot was caused by the used organism. The influ- 

 ence of temperature and moisture on these storage rots will be discussed 

 later. 



On January 16, 1914, four tubers were inoculated in the usual way 

 with D. tubericola from dasheen. By February 18 all were rotted and 

 the causal organism recovered in pure culture. The checks, two in num- 

 ber, remained healthy. 



On March 1, 19 14, twelve tubers were inoculated with D. tubericola 

 from dasheen. On March 12 several tubers showed evidence of decay 

 and by March 20 nine were partially rotted. A portion of some of the 

 tubers was black, and pycnidia containing hyalin 1 -celled spores were 

 present. On June 1 all the tubers were completely decayed. The 

 checks, five in number, remained sound. 



On January 14, 191 5, four tubers were inoculated with D. tubericola 

 from sweet potato. On February 18 all the tubers were rotted, and the 

 causal organism was recovered in pure culture. Two days later ten 

 tubers were inoculated and divided into two equal lots, one being placed 

 in an incubator, the temperature of which varied from 34 to 35 C, and 

 the other in an ice box, the temperature of which varied from 12 to 

 1 3 . By February 3 all the tubers in the incubator were rotted and 

 the causal organism was recovered in pure culture, while those in the 

 ice box and the five checks remained sound. 



On March 26 six tubers were inoculated with D. maclurae. Some time 

 later one was completely decayed and yielded D. maclurae in culture; the 

 others remained sound. Four more tubers were inoculated on May 13, 

 191 5, and on June 6 three tubers were half-decayed, D. maclurae being 

 recovered from two, Rhizopus nigricans from one, and Fusarium sp. 

 from one. The checks, five in number, remained sound. 



Six other tubers were inoculated on May 20, 191 5. On June 1 two 

 were completely decayed and four remained sound. 



On December 23, 1914, nine tubers were inoculated with D. gossypina, 

 five of which were placed in an open receptacle on the laboratory shelf 

 and four in a moist chamber. All the exposed tubers were rotted on 



