Kew Yokk Agricultural Experiment Station. 273 



ing spores in sterile water and spraying them on the young shoots 

 of several small vines. Contemporaneous germination tests of spores 

 in drops of water on glass slides gave 80 to 90 per ct. germination at 

 the end of 20 hours. The plants were entirely covered with bell 

 glasses for 24 hours. Infection was also favored by humid external 

 conditions. Other plants were sprayed with sterile water, but other- 

 wise subjected to the same treatment. They remained healthy. 

 In 30 days (June 20th) lesions became evident on the inoculated 

 plants and when they increased in size some of the stems were 

 completely involved. 



July 22d some of the infected shoots were sterilized externally by 

 immersing in mercuric chloride solution 1-1000. Thin shavings of 

 epidermis were removed with a sterile scalpel and bits of the under- 

 lying diseased tissue transferred to sterile grape steins in tubes and 

 to potato agar slants. August 5, 1913, the tubes were examined. 

 The Fusicoccum stage of the fungus had developed and was pro- 

 ducing spores in six of the ten grape-stem tubes. Two tubes were 

 sterile and one was contaminated. A similar growth of mycelium 

 appeared in five of the eight agar slants, and had the appearance 

 of the dead-arm fungus when grown on potato agar, two tubes 

 remained sterile and one was contaminated. 



Two things are of interest in connection with this experiment. 

 (1) The pure culture used for inoculation purposes had been kept 

 alive through successive generations in test tubes for five years. 

 At the end of that time it still retained its virulence as indicated 

 by the abundant infection obtained and by the appearance of lesions 

 after the characteristic period of incubation as noted under natural 

 conditions. (2) The susceptible parts of the vine are limited to the 

 tender, more succulent growth. The infected area on the shoots 

 inoculated was confined to about two internodes, but stem, leaf 

 petiole, leaf veins, tendrils when present, and apparently leaves 

 within this range bore lesions. Older parts were not affected. 



In the light of these experiments the failures in the earlier attempts 

 are readily understood. In addition to unfavorable atmospheric 

 conditions it appears that the host had passed the period of suscep- 

 tibility. The trial of July 12, 1910, was made under fairly favorable 

 conditions in that a heavy rain at 12 m. was followed by calm, cloudy 

 weather which permitted drops to cling to the canes. A quantity 

 18 



