66 RESEARCHES ON FUNGI 



at the average rate observed, then 8,000 spores would be set free 

 in 80 seconds, i.e. at the rate of 100 per second. This would be 

 sufficient to produce a thin continuous cloud such as one sees in a 

 beam of sunlight directed beneath an active fruit-body. 



The distance to which the ascospores are shot in still air, before 

 their velocity of propulsion is reduced to zero by the resistance 

 of the air, is from 0-5 to a little more than 1 cm. (Fig. 19, J). This 

 was proved by two experiments. In the first, a piece of pileus 

 having a superficial area of about 2 square cm. and a thickness 

 of 4 mm., was placed with the necks of the perithecia looking 

 vertically upwards in a large compressor cell. The lid of the 

 cell was then inverted and laid over the base in such a way that 

 the cover-glass of the lid was raised just 1 cm. above the necks 

 of the perithecia. The preparation was left undisturbed during a 

 night. Next morning it was found that a number of ascospores 

 had been shot up to the cover-glass and had stuck there, but that 

 the majority of the spores discharged from the asci were lying over 

 the perithecial stroma in the form of a white spore-dust. Since 

 newly-discharged ascospores always stick to glass when they strike 

 it, the experiment showed that, while some of the asci of the Hypo- 

 myces can shoot their spores 1 cm. or more high, the majority of 

 asci cannot do this. In a second experiment, a piece of pileus 

 was placed on the base of a van Tieghem cell so that the peri- 

 thecial layer was in a vertical plane, and then a cover-glass was 

 sealed on to the glass ring with vaseline. The preparation was 

 therefore arranged so that the asci would shoot out their spores 

 horizontally in still moist air and so that the spores, as soon as 

 the resistance of the air had reduced their propulsion velocity 

 to zero, would fall on to the horizontal base of the cell. After a 

 night had passed, the preparation was examined, and it was found 

 that the spore-deposit was thickest about 5 cm. from the peri- 

 thecial layer and that, proceeding away from this layer, the deposit 

 grew thinner and thinner until, at a distance of a little more than 

 1 cm., its limit was reached. From these experiments, we may 

 draw the conclusion that the spores are violently propelled from 

 the necks of the perithecia to a distance of from 0-5 cm. to 1 cm. 

 before their velocity of propulsion is reduced to zero by the 



