THE SPHAEROBOLUS GUN 



337 



larger than the fungus fruit-body and their seeds are heavier than 

 the glebai mass ; and it is probably safe to say that the Sphaero- 

 bolus fruit-body easily outranges any phanerogamic fruit of its own 

 size. 



The Horizontal Range of Expulsive Fruits. 



The Kinetics of the Sphaerobolus Gun. — In Sphaerobolus 

 stellatus, the distance from the bottom of the inside of the stellately 

 opened cup, upon which the glebai mass lies, to the top of the everted 

 inner peridial membrane when this forms a balloon-like covering 

 to the top of the cup after the glebai mass has been discharged (c/. 

 Figs. 136, 160, and 172, pp. 281, 315, and 361) is about 3 mm. Pressure 

 is therefore exerted upon the glebai mass before it leaves the gun 

 over a distance of about 3 mm. As the Sphaerobolus gun before 

 discharge is only about 2 mm. high, this distance is remarkably 

 great, and no doubt it is a main factor in making the Sphaerobolus 

 gun so efficient. 



It has been possible to measure or estimate : (1) the height to 

 which a Sphaerobolus projectile may be shot, (2) the diameter of 

 the projectile, (3) the specific gravity of the projectile, and (4) the 

 distance over which the propelling peridium acts on the projectile 

 before the projectile leaves the gun. 



With the help of the data just enumerated we shall first calcu- 

 late mathematically : (1) the initial velocity of the Sphaerobolus 



VOL. v. 



