TILLETIA TRITICI 267 



Examination of the cover-glasses in the whole series of experiments 

 showed that basidiospores were present upon them at all distances 

 up to 1 • mm. above the agar, but never at any greater height. 

 From the 1-0 mm. must be deducted 0-1 mm. for mycelial pro- 

 jection, as already explained. Hence it may be concluded that the 

 basidiospores of Tilletia tritici are shot upwards to a maximum 

 distance of about 1 mm. 



Only very few spores were shot to a height of • 9 mm., but there 

 were always many spores adherent to cover-glasses raised 0*5- 

 • 6 mm. above the agar. 



The maximum horizontal distance to which the basidiospores 

 of Tilletia tritici are shot from their sterigmata in still air was 

 determined as follows. 



A glass ring 17 mm. in diameter and 6 mm. high, from which a 

 piece of the side 11 mm. wide had been broken out, was placed on 

 the bottom of a Petri dish so as to assume the position shown in 

 Fig. 133, A, and the whole was then sterilised in hot air. Twenty 

 cc. of agar medium were then poured into the plate, care being 

 taken to keep the glass ring in the position shown in Fig. 133, A. 

 The medium soon solidified, and then the agar within the ring was 

 sown with basidiospores by the spore-fall method. To accomplish 

 this, a Petri-dish culture was inverted over the base of the dish 

 containing the ring, as shown in Fig. 133, A. The arrows in Fig. 

 133, A, indicate the path of fall of the basidiospores. The spores 

 were allowed to fall for three hours. The upper Petri-dish base (a) 

 was then removed, and the lower one (6) covered with its lid. The 

 basidiospores in the closed Petri dish (6) soon germinated and, 

 after 5-7 days, the mycelium had formed a thin white mat at the 

 surface of the agar. At the end of this time, with the aid of a 

 scalpel, the agar was cut downwards in planes coincident with the 

 two flat ends of the glass ring and then the ring, together with the 

 agar and mycelium contained within it, was lifted out of the dish 



Fig. 133 — cont. 



discharged basidiospores when viewed with the microscope through the base of 

 the Petri dish at the bottom of the ring shown in B after spore-discharge has 

 proceeded for 2-3 hours. The scale enables one to measure the horizontal 

 distance of discharge of the basidiospores. A and B, about natural size ; C, 

 magnification, about 56, 



