EXTERNAL CONDITIONS AND SPORE-DISCHARGE 129 



chamber of 0'75 litres capacity, through which a strong stream of 

 oxygen was made to flow for some minutes. The stop-cocks were 

 then closed. The pieces of pileus were set on glass slides so that any 

 falling spores might be caught. 



After an hour, apparently equally thick deposits of spores had 

 been shed both in air and in the pure oxygen. The half-pilei were 

 then placed in new positions on the glass slides. During this opera- 

 tion air was kept out of the oxygen chamber by means of a strong 

 stream of oxygen passed through it. Five hours subsequently the 

 new spore-deposits Avere examined. They appeared to be equally 

 thick in both air and pure oxygen. The half-pilei were again 

 placed in new positions on the glass slides. These were once more 

 examined after an interval of eighteen hours. Heavy spore-deposits 

 resembling each other had again formed both in the air and in the 

 oxygen. 



This experiment seems to prove that, in an atmosphere of pure 

 oxygen, the fruit-bodies of the two species examined continue to 

 develop their basidia and to shed their spores in the usual manner. 

 This need not occasion surprise, for many even of the higher plants 

 develop normally in pure oxygen or under a pressure of five 

 atmospheres of air.^ 



The Effect of Anaesthetics. — An observation with an anaesthetic 

 has already been made by Falck. He found that a fruit-body of 

 Agaricus nebularis, on being subjected to chloroform vapour, 

 ceased to shed spores, and he drew the conclusion from this fact 

 that spore-liberation is an active process.- Experiments with 

 anesthetics, hoAvever, do not decide whether the spores are set 

 free by a process of growth and thus simply fall when ripe like 

 apples, or whether, on the contrary, they are shot outwards from 

 their sterigmata with force. In the next chapter this matter will 

 be dealt with in detail. 



In order to test the effect of ether vapour upon the liberation 

 of spores, the following method was resorted to. A piece of cork 

 was 'fixed by means of sealing-wax \to the middle of a circular 



^ Pfeffer, Physiology of Plants, vol. i. p. 540. 



^ R. Falck, "Die Sporenverbreitung bei den Basidiomyceten,'' Beitrage zur 

 Biologie der Pflany.en, Bd. IX., 1904, p. 27, footnote. 



I 



