24 RESEARCHES ON FUNGI 



diameter varies from 1 ^ in the large basidia of Coprinus sterquilinus 

 to about 0-25 /* in species with very minute basidia. In Psalliota 

 campestris the diameter is about 5 /A. 



(3) The successive and not simultaneous discharge of the four 

 spores. 



(4) The maintenance of the turgidity of the basidium-body 

 during the successive discharge of the spores. 



(5) The non-collapse of the sterigma immediately after it has 

 discharged its spore. 



(6) The excretion of a drop of water at the hilum as an invariable 

 preliminary to spore-discharge. 



(7) The carriage of the water-drop with the spore when this is 

 shot away. 



(8) The fact that a spore does not burst but remains turgid when 

 it is violently broken off its sterigma, at a time when the canal 

 through the spore-membrane leading down to the sterigma is still 

 open. 



(9) The minute diameter of the canal through the spore- 

 membrane and sterigma. 



It may be regarded as certain that the mechanism for the 

 discharge of each spore is localised at the end of each sterigma, and 

 that the four sterigmata, so far as spore-discharge is concerned, act 

 independently of one another. It is at the hilum that the force 

 applied in the discharge of a spore becomes developed and effective. 

 The hilum, since it excretes a drop of water of relatively consider- 

 able size in from 5 to 10 seconds just before spore-discharge, 

 evidently is able to control the passage of fluid through its 

 membrane. 



It is possible that a spore is shot from its sterigma by 

 hydrostatic pressure. It may be that, at the hilum, water is 

 pumped into a small place by the protoplasm and that, when the 

 hydrostatic pressure is increasing in this small space, a certain 

 amount of the water escapes in the form of the drop which has 

 already been described. Possibly the drop weakens the cell-wall 

 on which it rests by acting chemically or physically upon it. We 

 may then suppose that, when the membrane has thus been 



