438 Journal of Agricultural Research voi. xiii. N0.9 



The Actinomyces was capable of producing a lesion the appearance of 

 which resembled pox. In January, 191 5, the writer severed his rela- 

 tionship with the Delaware Experiment Station, and assumed his present 

 position. A project on sweet-potato diseases was at once undertaken 

 at the Texas Agricultural Experiment Station. Pox was found to be as 

 serious a disease in Texas as in Delaware. Greenhouse work was there- 

 fore undertaken as it was not difficult to obtain "sick" soil both from 

 Texas and Delaware. Unfortunately, however, the field work was in- 

 terrupted that season. At the Delaware Station Dr. J. A. Elliott con- 

 tinued the work of the writer on sweet-potato diseases. He (j, 4) veri- 

 fied the writer's previous conclusion that the fungus A. batatas was 

 not the cause of pox. He further found that the disease was in- 

 duced by a myxomycete of a new genus and species which he named 

 " Cysiospora batata Elliott." The object of the present paper is to verify 

 Elliott's conclusions, and to add the observations and studies made by 

 the writer. 



NAME OF THE DISEASE 



The term "soilrot" given by Halsted (5) is appropriate only in so 

 far as it indicates that infection takes place on the underground portion 

 of the plant. But it suggests practically nothing as to the nature or 

 symptoms of the disease. In New Jersey the trouble is known to growers 

 of sweet potatoes as "groundrot," a name more suggestive than "soil- 

 rot." In Delaware the nature of the disease was only vaguely under- 

 stood; hence, it was variously known as "bugsting," "wormhole," 

 "fertilizer-bum," and was often mistaken for blackrot. In Texas the 

 disease has no definite name, but it is variously confused with the many 

 root troubles of the sweet potato. In Virginia the disease is known to 

 growers as "pox," or "pit," terms which best describe the trouble, and 

 which were adopted first by the writer (ij) and later by Elliott (j, 4). 



GEOGRAPHIC DISTRIBUTION 



There seems no doubt that pox has a wider geographical distribution 

 than is at present known. It can probably be found wherever sweet 

 potatoes grow. In New Jersey, Halsted (5) recorded it as a very serious, 

 well-distributed disease. In Delaware it is as yet localized to Kent 

 County, but appears to be gradually spreading southward. In Virginia 

 the pox, although widespread, is at present localized in small areas. In 

 Maryland the disease was recorded by Townsend (14) , and was found by 

 the writer to be a serious trouble, vying in importance with blackrot. 

 In South Carolina pox was reported by Barre (j). In Texas it had been 

 previously reported by Price {11) ; and from the writer's own observation, 

 pox is a serious disease in this State. The same trouble seems also to be 

 prevalent in Alabama, where it was recorded by Wilcox (13), and in 

 Oklahoma as reported by Learn (9). The disease is also prevalent in 

 Kansas, Prof. L. E. Melchers having recently sent specimens of it to 

 the writer. 



