796 



SCIENCE 



[N. S. Vol. XXXI. No. 803 



Very little is j-et known respecting the methods 

 of natural infection or the period of incubation. 

 I am inclined to think, however, that the infec- 

 tion takes place several weeks before there is anv 

 general indication of the disease in the fields, and 

 possibly dates from the time of transplanting. 



Sulphur Injury io Potato Tubers: Mr. W. A. 

 Orton and ISIiss Ethel C. Field, Bureau of 

 Plant Industry. 



This paper is the outgrowth of experiments 

 conducted in California in 1909 for the control of 

 potato scab. Among other substances flowers of 

 sulphur was used in varying quantities to disin- 

 fect soils where the scab fungus was present. On 

 digging the crop, many tubers from the sulphured 

 rows showed sunken, dark spots from 5 to 30 mm. 

 in diameter, which were relatively free from 

 fungous or bacterial infection. These spots oc- 

 curred only in tubers from sulphured rows. They 

 were more numerous in the heavily sulphured 

 plots, but were present even where the seed piece 

 had merely been dipped in sulphur. Potatoes 

 exposed to sulphur fumes in the laboratory devel- 

 oped similar depressed spots. 



This injury has apparently not been observed 

 in the sulphur experiments conducted in the east. 

 The California soils are peat and in late fall 

 became quite dry near the surface, so that vola- 

 tilization of the sulphur could easily have oc- 

 curred. 



Outbreak of Potato Canker {Chrysophlyctis endo- 

 biotica Schilb.) in ^Newfoundland, and the 

 Danger of its Introduction into the United 

 States: Dr. H. T. Gussow, Central Experi- 

 mental Farm, Ottawa. 



This well-known European potato disease has 

 been recognized in specimens which I received 

 from Red Island, Placentia Bay, N. F. The dis- 

 ease is due to a fungus of the order Chitridinete 

 and -was named by its discoverer. Professor Schil- 

 bersky, in 1896, Chrysophlyctis endobiotica. The 

 fungus attacks the tubers, but eases have been 

 observed where the leaves closely above ground 

 were also attacked. The changes due to the 

 fungus on the tubers are very characteristic. 

 Unfortunately the disease is not noticeable in the 

 field until the crop is harvested, when it will be 

 shown that the tubers are covered— according to 

 the severity of the attack— either at the eyes only, 

 or half or wholly by peculiar excrescences, not 

 unlike the common crown galls of fruit trees. 

 When a tuber is wholly covered with these excres- 

 cences they have lost all resemblance to potatoes 



and appear like irregular lumps of clay or coke. 

 The fungus lives in the cells of these excrescences, 

 which are not covered by the epidermis. It is 

 present in these cells, first, as a more or less free 

 Plasmodium; second, as hyaline globular bodies, 

 enclosed by a thick membrane and third, as yel- 

 lowish brown resting spores very similar in ap- 

 pearance to those of the Peronospor*. This 

 latter stage is the most common one. The spores 

 are very difficult to germinate artificially. Suc- 

 cessful germination test showed that the spores 

 burst and numerous swarm spores were liberated. 

 These swarm spores infect new cells passing 

 through the different stages — all of which are 

 unsatisfactorily known — indeed it is doubtful 

 whether there is any justification for the new 

 generic name as described. The tubers decay by 

 the action of the parasite and when harvested 

 break to pieces and thus the soil becomes infected. 

 The disease made its appearance in 1901 in Eng- 

 land, is now present in Ireland, Scotland, Scan- 

 dinavia, Germany and other European countries, 

 but was not, until its discovery in Newfoundland, 

 known on this side of the Atlantic. A visit to 

 Newfoundland led to the discovery of the disease 

 all over the neighborhood, and subsequently it 

 was found to exist in other localities as well. 

 As it was pointed out to me on inquiry that 

 potatoes were imported in small quantities to the 

 United States and Canada, great precaution is 

 necessary to prevent the introduction and estab- 

 lishment of this serious pest. On account of the 

 dangerous nature of the disease it was recom- 

 mended that immediate action should be taken to 

 safeguard the interest of the American and 

 Canadian farmers, and a committee be appointed 

 to consider the best means of dealing with the 

 possible danger from its introduction into the 

 United States. The fungus has also been referred 

 to as CEdomyces leproides Trabut, but it is 

 very different from this fungus, which according 

 to Magnus is synonymous with Synchytrium 

 putxosani. 



Rhizoctonia Stem Pot of Beans: Mr. M. J^. Bab- 

 bus, Cornell University. 



While working on bean diseases in the vicinity 

 of Oneida, N. Y., during the summer of 1909, 

 quite a large percentage of plants were noticed to 

 be affected with a disease which caused cankers on 

 the parts of the stem below or at the surface of 

 the ground, these lesions frequently encircling the 

 stem, causing it to break over and resulting in 

 the death of the plant. In some fields as much 

 as 30 per cent, of the plants became thus affected. 



