1016] PARASITIC RHIZOCTONIAS IN AMERICA 353 



seedlings, produced practically 100-percent infection in the case of 

 cabbage seedlings (Fig. 19). 



In the third group, beet, radish, and turnip seedlings proved very 

 susceptible to damping-off of Rhizoctonia. It is rather interesting to 

 observe that while the strain from radish was able to cause only 

 1-percent infection of radish seedlings, it caused almost 100-percent 

 infection of turnip seedlings. 



Taking the experiment as a whole, it is seen that a great variation 

 exists in susceptibility of seedlings and in virulence of strains. It is 

 clear that under certain conditions all the strains can attack a given 

 host with about the same virulence. 



EXPERIMENT 8: INOCULATION OF VARIOUS HOSTS (OLD) OTHER THAN 

 CARNATION WITH VARIOUS STRAINS OP RHIZOCTONIA 



In Experiment 8 the preceding experiment was carried one step 

 farther, older plants being used rather than seedlings. A number of 

 plants were taken from flats while small and transplanted to four-inch 

 pots, where they were allowed to grow for about two months. The 

 soil in these pots was not sterilized. Each plant, with the exception of 

 the check plants, was inoculated by placing an infected bean plug in 

 contact with it just below the surface of the soil. Four kinds of 

 plants, 50 of each, and 12 strains were employed. The observations 

 from this experiment are recorded in Table 10. 



In Group 1, the tomato plants proved resistant to the attacks of 

 the various strains, with the exception of the one from carnation, which 

 produced a slight infection on two plants. In the case of the cabbage 

 plants, the strains from cotton and from cauliflower exhibited a marked 

 specialization, producing 50- and 90-percent infection, respectively, on 

 these plants, while on tomato plants they produced no infection what- 

 ever. Cabbage was the only host in the experiment susceptible to all 

 the strains with which it was inoculated. 



The carnation strains in Groups 2 and 3 also proved more virulent 

 than the other strains, producing 50-percent infection on lettuce and 

 100-percent infection on beet (Fig. 9). Of the other strains, eggplant 

 alone was able to attack the plants, producing a slight infection on 

 two lettuce plants. 



EXPERIMENT 9: INOCULATION OF VARIOUS HOSTS (CUTTINGS, SEED- 

 LINGS, AND LARGER PLANTS) WITH VARIOUS STRAINS OF RHIZOCTONIA 



The kinds of plants used in the foregoing experiments were some- 

 what limited. Increased facilities being at hand in the spring of 1914, 

 a more extensive series of inoculations was made with cuttings, seed- 

 lings, and larger plants of various kinds. In all, about 350 cuttings, 

 3,000' seedlings, and 300 larger plants were inoculated. Thirty-two 

 strains of Rhizoctonia were used. 



