258 RESEARCHES ON FUNGI 



added on Puff-balls. In the genus Lycoperdon, 1 the fruit-bodies 

 develop an enormous number of spores, and at maturity con- 

 stitute sacs full of a dry powder mixed with capillitium 

 threads. The peridium breaks away above so that each Puff- 

 ball conies to have a more or less circular opening at the 

 top. The arrangement is such that the spores leave a fruit-body 

 only when the wind is blowing at a favourable speed for their 

 dispersion. When the air is quiet, the spores lie safe and motion- 

 less within the protecting peridium. As soon, however, as the 

 wind becomes violent, it sweeps in gusts into the Puff-ball from 

 above, gradually disengages the spores from the capillitium 

 threads, and bears them forth to long distances. A more 

 effective mode of spore -dispersion can scarcely be imagined. 

 In connection with Puff-ball spores an interesting physical prob- 

 lem awaits solution. We are still ignorant why it is that the 

 spores of Hymenomycetes never form a mass of loose dust, 

 whereas this regularly occurs with those of a Lycoperdon. The 

 adhesiveness or non-adhesiveness of spore cell-walls must be 

 recognised as a matter of importance in connection with spore- 

 dispersion. 



The Sound produced by the Discharge of Spores, with 

 Special Reference to Pilobolus. Although many Agarics which 

 have come under my notice shed spores at the rate of about 

 a million a minute, I have never been able to detect the least 

 sound caused by spore-discharge. So far as unaided human ears 

 are concerned, it seems likely that spore-emission by Hymenomy- 

 cetes must for ever be a quite silent process. On the other hand, 

 the discharge of spores by certain Ascomycetes appears to be 

 distinctly audible. Thus de Bary was able to hear "a very per- 

 ceptible hissing sound produced by strong specimens of Peziza 

 acetabulum and Helvetia cr-ispa." 2 



Pilobolus, as is well known, exceeds all Ascomycetes in the 

 violence with which it ejects its projectiles. Coemans records 

 that the sporangia can be projected to a height of over 



1 Vide Chap. V. p. 86. 



2 De Bary, Comparative Morphology and Physiology of the Fungi, etc., English 

 translation, 1887, p. 92. 



