BLACKLEG. 317 



plants are pointed out to them will say that they have seen occa- 

 sional hills showing this trouble several years past, but have 

 looked upon it as something of minor importance. Usually 

 the period given varies from 5 to 10 years, but ]\Ir. Borden 

 Blackstone of Perham assures the writer that 30 years ago he 

 observed something which he believes to be identical with this. 



Partly Decayed Seed Tubers Spread the Disease. 

 In an attempt to artificially inoculate seed tubers in the spring 

 of 1909 three bushels of tubers, Green Mountain variety, w^ere 

 used. One bushel was planted as purchased. The tubers of 

 the other two bushels were liberally sprayed with a living, viru- 

 lent culture of the bacteria which cause the disease. They were 

 allowed to dry off wdiile spread on the floor under an open shed 

 away from direct sunlight, and covered lightly with builder's 

 paper. Then one bushel of these latter was soaked in formal- 

 dehyde solution as is customary in treating for scab.'^ About a 

 week later all three lots were planted. There was a good stand 

 on all three plots, and no blackleg was observed on any of them. 

 This was somewhat surprising in view of the experience of the 

 previous year which was as follows : — Attempts to isolate the 

 specific organisms from plants growing at a distance of from 

 50 to 100 miles from the laboratory, generally with the disease 

 in the later stages when found, only resulted in failure during 

 1907, and the early part of the summer of 1908. Then recourse 

 was had to the following method. Seed tubers bearing short 

 sprouts were planted in boxes on July 25. Before planting the 

 tubers were wet with a watery extract made by crushing some 

 diseased stems, and, after planting, this extract was poured over 

 the soil above. On August 18 several of the young stems 

 from these tubers showed well developed cases of blackleg. 

 From these virulent organisms were isolated with ease. In this 

 connection it should be said that the tubers in the boxes were 

 kept constantly quite wet while the land on which the culture- 

 sprayed tubers were planted in 1909 was exceedingly dry for 

 some weeks following. Later experiments showed that the 



* Soaked 2 hours in a solution consisting of 8 fluid ounces of formalin 

 (40% solution) formaldehyde and 15 gallons of water. 



