270 



RESEARCHES ON FUNGI 



and then thoroughly washed in sterile water. Immediately there- 

 after they were placed on the surface of sterilised greenhouse-soil 

 held in a Petri dish, and then they were inoculated by means of the 

 spore-fall method. The falling basidiospores were derived from 

 (1) a vigorous test-tube culture, like that shown in Fig. 121 (p. 249), 

 or (2) a vigorous plate culture, like that shown in Fig. 119 (p. 246). 

 The whole apparatus was kept at a temperature of 10°-13° for 6-8 

 days, during which time secondary basidiospores were falling in 

 large numbers on to the slowly developing seedlings. At the end of 

 the inoculation period, the seedlings, together with attached soil, were 

 carefully removed from the Petri dish and were placed on the surface 

 of sterilised greenhouse-soil in a 6-inch pot, and then the soil was 

 heaped upon their basal portions, care being taken not to injure the 

 root system in any way. The pots were set in a cool greenhouse 

 (about 15° C.) for the first three or four weeks and in a warmer 

 situation subsequently. After about three months, when the 

 plants were matured, the results of the experiments could be deter- 

 mined by observing whether or not the heads had become bunted. 

 When a plant produced bunted heads, its chlamydospores were 

 examined with the microscope and it was always found that the 

 chlamydospores belonged to the same species as that which had 

 been used for the inoculum. 



Infection of Germinating Wheat Seedlings by the Secondary Basidio- 

 spores of Tilletia tritici and T. laevis. 



