. Carnegie Institution of Washington publication. i8o BACTERIA IN RELATION TO PLANT DISEASES. In 1901 the writer again obtained successful infections. The plants inoculated were potato, tomato, etc. The source of infection was a tomato plant received that summer from South Carolina. The inoculations were by means of needle-pricks on leaves and the upper parts of growing shoots. The infectious material was fluid from the bottom of slant agar- cultures (the first subcultures from colonies on poured plates). The period of incubation varied from 3 to 7 days. Successful inoculations were made in th
. Carnegie Institution of Washington publication. i8o BACTERIA IN RELATION TO PLANT DISEASES. In 1901 the writer again obtained successful infections. The plants inoculated were potato, tomato, etc. The source of infection was a tomato plant received that summer from South Carolina. The inoculations were by means of needle-pricks on leaves and the upper parts of growing shoots. The infectious material was fluid from the bottom of slant agar- cultures (the first subcultures from colonies on poured plates). The period of incubation varied from 3 to 7 days. Successful inoculations were made in the summer of 1903 with pure cultures obtained from a diseased potato plant gathered at Norfolk, Virginia. Inoculations were carried out successfully in 1904 on tomatoes, potatoes, etc., with pure cultures obtained from a potato- plant growing in the District of Columbia, near Washington. Partially successful inocu- lations were carried out in 1905 on potatoes with pure cultures obtained from a tomato stem received from Florida (vol. I, pis. 24 and 25), and on tomatoes with subcultures of colonies plated from Florida pota- toes. For details concerning these results and for the various failures see synopsis of the in- oculations. Plants in the field are attacked in all stages of growth. There seem to be, how- ever, varietal dif- ferences in suscep- tibility as well as great individual differences. The writer succeeded in pro- ducing the disease by allowing the Colorado potato- beetle (Doryphora TO-lineata) to feed on diseased plants and then transferring them for a few hours to healthy plants. The beetles were obtained from healthy potato fields where the disease did not afterwards appear, and the only possible source of infection was the diseased potato leaves and stems on which they were fed, and which were the result of pure-culture inoculations. The interior of these leaves and stems swarmed with bacteria and it was impossible that the mouth-parts of the beetles should not hav
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