126 CKOWN-GALL OP PLANTS. 



Five days later this experiment was repeated, exposing 1| and 2 

 hours. At the end of 2 days there were colonies only on the control 

 plate. Two days later colonies appeared also on the 1^-hour plate, 

 but none on the 2-hour exposure. Daisy plants sprayed with this 

 strength of solution were not injured. 



Formalin. — In September, 1907, tests were made in formalin 

 diluted with water (1:500), exposing 10, 20, 30, 40, and 60 minutes. 

 Colonies were abundant in all the plates except the 60-minute expo- 

 sure, which 3delded onl}^ a few. 



Suspecting the strength of the formalin used, this experiment was 

 repeated in May, 1910, as follows: 



Transferred two 3-mm. loops of a 2-day-old bouillon culture to 

 10 c. c. of formalin in distilled water (1 : 500). This formalin solution 

 was made from a freshly opened stock bottle. A check was made by 

 transferring one loop from the bouillon tube to 10 c. c. of sterile 

 water and pouring 2 plates. 



The plates of the organism exposed to the formalin were poured 

 at intervals of 10, 20, 30, 40, and 60 minutes. 



Results: May 26, the plates are free from colonies. May 27, the 

 plates are free from colonies. May 28, the check plates have numer- 

 ous tiny colonies; the others are free. May 31, a few colonies up on 

 the 10-minute plates; the others are free. June 4, colonies appeared 

 only on the plates made from the 10-minute exposure. 



Mercuric chloride. — Tests were made in a water solution of mercuric 

 chloride (1:10,000), exposing 15 minutes, 30 minutes, and 5 hours, 

 with a check plate of the organism from a suspension in distilled 

 water. After 3 days there were numerous colonies on the check 

 plate but none on the others and none appeared later. 



PATHOGENICITY. 



This organism was first isolated from galls occurring on the hot- 

 house daisy ( Chrysanthemum frutescens) , but it causes, at least by 

 inoculation, tumors in plants of many families, viz, Compositae, 

 Solanaceae, Oleaceae, Umbelliferae, Vitaceae, Leguminosae, Rosaceae, 

 Cruciferae, Caryophyllaceae, Chenopodiaceac, Urticaceae, Juglanda- 

 ceae, Salicaceae. 



LOSS OF VIRULENCE. 



In cultures earned on for several years a slow gradual loss of viru- 

 lence has been observed, but this was not detected until after the 

 second year. 



GROUP NUMBER. 



The group number according to the descriptive chart, Society of 

 American Bacteriologists, is: 212.2322023. 



213 



