324 RESEARCHES ON FUNGI 



in one-fifteen-hundredth to one-thousandth part of one second 

 and, in so doing, attains a final axial velocity of 20-30 feet per 

 second. 



The tooth-tip adhesion of the two sets of peridial membranes is 

 doubtless of considerable importance for the efficient working of the 

 Sphaerobolus gun ; for, if the two sets of membranes were to break 

 apart at the moment when the inner set had attained its maximum 

 state of eversion, the inner set of membranes would follow after the 

 projectile and interfere with its flight. 



Occasionally, at the moment of discharge of the projectile, the 

 inner set of membranes does actually break away from the outer 

 set and travel for a few inches through the air ; but the rarity of 

 this phenomenon indicates that it is due to some unusual imperfection 

 in the development of the fruit-body. 



The tooth-tip mode of attachment of the inner and outer sets of 

 membranes is such that the inner set, when everting, is given the 

 maximum possible working distance for pressing against the pro- 

 jectile. It is this long working distance — about 3 mm. — which in 

 a large degree is responsible for the high efficiency of the Sphaero- 

 bolus gun. 



As the eversion of the inner set of membranes takes place during 

 the discharge of the gun, the openings between the sinuses of the 

 inner and outer teeth become diamond-shaped (Fig. 147, C, p. 298). 

 At the same time, air rushes through these openings into the 

 enlarging central cavity of the fruit-body and thus the formation of 

 an internal vacuum which would interfere with the efficient working 

 of the gun is prevented. The air-passage function of the diamond- 

 shaped openings will be further treated of in the Section on the 

 kinetics of the gun. 



The outer non-everting set of membranes is of importance for 

 the working of the Sphaerobolus gun in that it fixes the gun to a 

 substratum, holds the inner set of membranes by its periphery as 

 it everts, and prevents the inner set of membranes from following 

 after the projectile and interfering with its flight. 



The slimy liquid which collects in the stellately opened Sphaero- 

 bolus fruit-body just before discharge and which wets and partially 

 submerges the glebal mass (Fig. 161, B, p. 316) has already been 



