1916] PARASITIC RHIZOCTONIAS IN AMERICA 349 



On September 1, 1913, the soil in two five-foot sections in the green- 

 house was sterilized, and twenty carnation plants from the field were 

 placed in each section, four plants in a row. Four rows in each sec- 

 tion were each inoculated with a different strain of Rhizoctonia, by 

 means of pieces of infected bean plugs. The middle row in each sec- 

 tion was left as a check. 



The plants began to die off at the end of three weeks and con- 

 tinued dying until the close of the experiment, October 31. They all 

 died in a manner characteristic of stem rot. All the strains used 

 proved to be virulent except the one from beet (see Table 7). The 

 check plants remained healthy thruout the experiment. 



TABLE 7. SUSCEPTIBILITY OF OLD CARNATION PLANTS (IN THE BENCH) TO 



VARIOUS STRAINS OF RHIZOCTONIA: EXPERIMENT 5 



Strain (Healthy | Diseased 



The high mortality of the strains in this experiment was due, to a 

 large extent, to the date of inoculation. The plants in the preceding 

 experiments were inoculated either late in the fall or in the early 

 spring, when the temperature in the greenhouse was low and normal 

 and not influenced by outside conditions. The temperature in the 

 house during September and October, when these plants were inocu- 

 lated, is very high ; hence the virulence of the fungus was much greater. 

 The effects of inoculating plants at various times of the year are 

 clearly brought out in the next experiment. 



EXPERIMENT 6: INOCULATION OF CARNATION PLANTS WITH RHIZOC- 

 TONIA AT DIFFERENT TEMPERATURES 



During the season 1913-14 a number of sections containing carna- 

 tions were reserved in the greenhouse, and at different times of the 

 year the plants were inoculated with Rhizoctonia from carnation. 

 This experiment was for the purpose of ascertaining the relative 

 virulence of Rhizoctonia when inoculated on carnation plants at dif- 

 ferent temperatures. 



Each section contained twenty plants, sixteen of which were in- 

 oculated by placing infected bean plugs at the base of the stem. The 

 remaining four plants served as checks. 



