THE SPHAEROBOLUS GUN 345 



Momentum of a projectile shot 14- 5 feet high, 



when leaving the gun 0- 00008 units. 



Kinetic energy of a projectile shot 14- 5 feet high. 



when leaving the gun 0- 000037 foot pounds. 



Average force of the propelling peridium, 



when acting on the projectile 0-13 poundals, 



or 0- 004 pounds. 



Rate of developing energy in a Sphaerobolus gun which shoots a 



projectile 14- 5 feet high - horse power. 



r J 6 10,000 * 



Relations of Sphaerobolus with Water. — Without a sufficient 

 supply of water the Sphaerobolus gun can neither open stellately 

 nor, if opened stellately, discharge its projectile. As explained in 

 an earlier Section, this is due to the fact that the force employed 

 in the opening and discharge of the gun is, in the main, the osmotic 

 pressure in the cells of the palisade layer of the peridium. 



The unopened fruit-bodies of Sphaerobolus stellatus can withstand 

 desiccation for several months without any loss of vitality. Thus 

 a piece of wood bearing young fruit-bodies was collected at Minaki 

 (western Ontario) in the summer of 1928, was allowed to become air- 

 dry in the laboratory at Winnipeg and, after having been kept dry 

 for about four months, was re-moistened ; whereupon the fruit- 

 bodies at once revived, continued their development, and eventu- 

 ally discharged their glebal masses. This revival after desiccation 

 is a phenomenon exhibited by the fruit-bodies of Schizophyllum, 

 Panus, Corticium, Stereum, Dacryomyces, Calocera, and many 

 other Basidiomycetes which grow upon sticks and other masses of 

 wood, i.e. upon a substratum which rapidly dries up in dry weather 

 and readily re-absorbs water when precipitation occurs. It is 

 certain that, under natural conditions, the fruit-bodies of 

 Sphaerobolus stellatus often persist through periods of summer or 

 autumn drought in a desiccated condition and, subsequently, upon 

 the advent of rain, absorb water rapidly, revive, and continue their 

 development. 



When pieces of wood or dung containing the mycelium of 

 Sphaerobolus stellatus are collected in the open or when artificial 



