190 Journal of Agricultural Research voi. v, no. s 



was Idaho Rural. However, many of these Avere almost completely 

 destroyed, being very mush^- and "leaky. "^ The organism was 

 recovered from all varieties, two reisolations being made from the 

 Rurals. 



F. oxysporum 2999; isolated on March 14, 19 14, from a tuber with 

 wound-invading brownish dry-rot from Brookings, S. Dak. Culture, 

 16-day-old pionnotes on stem of Melilotus alba. The results were the 

 same as with strain 2997. The organism was recovered in all attempts, 

 reisolations being made from all varieties except Early Rose. 



F. oxysporum 3045; a reisolation of strain 2997 from a rotted tuber 

 of the Idaho Rural variety 20 days after inoculation at 23.1° C. After 

 incubating for 21 days at an average temperature of 25.6° C. all tubers 

 of all varieties — i. e.. Netted Gem, Idaho Rural, and People's — showed 

 a deep, progressive rqt, a brown zone about the inoculation prick 

 surrounded by a water-soaked area more or less brown in color. The 

 organism was recovered by three isolations. 



In a subsequent trial with strain 3045, inoculating the four varieties 

 Idaho Rural, Netted Gem, Burbank, and Pearl with a i -month-old 

 culture on a stem of Melilotus alba and incubating for 37 days at an 

 average temperature of 20.4°, similar results were obtained. Seven 

 reisolations were identified from this lot. 



F. oxysporum 1948; isolated and identified by Dr. Wollenweber from 

 a secondary rot following infection by Phyiophthora infestans. Material 

 from Honeoye Falls, N. Y., February, 191 3. Culture used was i month 

 old on stem of Melilotus alba. The results at different incubation 

 periods and temperatures are as follows: Ten tubers incubated for 24 

 days at an average temperature of 24.6° rotted, four slightly decaying 

 in all punctures and six wet-rotting. Organism recovered. One tuber 

 at 18.4° rotted in 51 days, while one at 17.8° failed to decay in this 

 time, but the organism persisted. 



F. oxysporum 2413; isolated and identified by Wollenweber in January, 

 i9i3,from a potato of the Up-to-Date variety, grown on Potomac Flats, 

 Washington, D. C, in 1912, affected with the ring disease. Cultures used, 

 one on stem of Melilotus alba and one on a potato cylinder 25 days old. 

 Result of incubation at 25.7° C. for 14 days: All inoculated tubers de- 

 cayed, 50 per cent being very badly decomposed with wet-rot; organism 

 recovered by four reisolations. Two tubers incubated at 17.8° and 18.4°, 

 respectively, for 51 days suffered a rather dry rot; organism recovered. 



F. oxysporum 3395; reisolation of strain 2413 from badly rotted Green 

 Mountain potato tuber. Culture used, 4-day-old potato cylinders. 

 Owing to the fact that certain of the tubers were rotting badly, the 

 experiment was concluded before some of the others had started to decay. 

 All of the Pearls, 95 per cent of the Netted Gems, and 50 per cent of the 



' Orton (9, p. 11) described a soft-rot caused by Rkizopus nigricans. Potatoes affected with this disease 

 are called " leaky" or " melters," 



