SPORE-DISCHARGE FROM POLYPOREAE 105 



contrary to what I should expect ( 1 ) from my beam-of-light studies 

 of spore-discharge in Polyporeae and Agaricineae, and (2) from my 

 microscopic studies of the organisation of the hymenium in the 

 Hymenomycetes generally. When a beam of light is directed 

 beneath the pileus of any fruit-body liberating spores, one can 

 see the spores as points of light with the naked eye ; and then one 

 can observe directly that the spore-stream coming from beneath 

 the pileus is remarkably constant in density. 1 I have examined 

 a large number of fruit-bodies in this way and can state that I 

 have never once found an exception to this rule. Never have I 

 found a fruit-body in which there was a rapid discharge of spores 

 for a few seconds or a minute or two and then a pause of a few 

 seconds or minutes before spore-discharge recommenced. I am 

 strongly inclined to believe that if Hydnum septentrionale were to 

 be tested by the beam-of-light method, it would be found to dis- 

 charge its spores in the same regular manner as other Hymeno- 

 mycetes. The slight irregular air-currents playing about such a 

 large fungus-mass as Banker observed in the open are invisible to 

 the naked eye and can only be revealed by the movements of the 

 spores which, falling downwards very slowly by their own weight, 2 

 are passively carried away by them. One cannot predict how these 

 tiny air-currents will move in respect to either speed or direction ; 

 and, in my judgment, it was only their irregularity and inter- 

 mittency which gave the impression to Banker that spore-discharge 

 from his Hydnum septentrionale was irregular and intermittent. 

 Finally, I have studied microscopically the production and libera- 

 tion of spores from certain Hydneae, although not from the species 

 in question, and have come to the conclusion that they take place 

 as in the Agaricineae where the basidia come to maturity in constant 

 succession, discharge their spores as soon as they are ripe, and 

 thus cause a certain number of spores to be liberated from every 

 square millimetre of hy menial surface per minute. 



The Vernal Spore-fall Period of Fomes fomentarius. Mycologists 

 have long been much puzzled how and when certain species of 



1 Vide these Researches, vol. i, 1909, p. 96. 



2 The rate of fall of spores of Hymenomycetes hi still air varies according to 

 their size and moisture contents. In many species it is only 1-2 mm. per second 

 and sometimes less than 1 mm. Vide these Researches, vol. i, 1909, p. 175. 



