THE SPHAEROBOLUS GUN 363 



tinous ring, and in part by the wall of the columella. The eight 

 spores of the projectile of Ascobolus immersus are held together by 

 their insoluble gelatinous outer cell-walls. The numerous spores 

 and gemmae in the projectile of Sphaerobolus cannot gain their 

 freedom because they he embedded and immobilised in a dense fatty 

 matrix upon which rain-water has no action. 



(6) Occurrence of the Gun-developing Fruit-bodies on the Dung 

 of Herbivorous Animals. The fruit-bodies of most species of Pilo- 

 bolus, e.g. P. longipes and P. Kleinii, occur exclusively on the dung 

 of herbivorous animals, such as the horse, the cow, and the rabbit. 

 Ascobolus immersus occurs on the dung of the cow, the horse, the 

 stag, and the sheep. 1 Sphaerobolus, as already recorded, is known 

 to occur on the dung of the elephant, the horse, the cow, the hare, 

 and the rabbit, so that there is plenty of evidence to show that 

 Sphaerobolus, like Pilobolus and Ascobolus immersus, is well fitted 

 for a coprophilous mode of existence. 



(7) Correlation of Facts. In Pilobolus, in Ascobolus immersus, 

 and in Sphaerobolus we can correlate : (1) the massiveness and 

 parabolic trajectory of the projectile, (2) the great violence in the 

 discharge of the projectile, (3) the adhesiveness of the projectile, 

 (4) the positive heliotropism of the fungus gun, (5) the multisporous 

 nature of the projectile and the non-separation of the spores whilst 

 the projectile is attached to herbage, and (6) the occurrence of the 

 gun-developing fruit-bodies on the dung of herbivorous animals ; 

 for they are all factors associated with the dissemination of the spores 

 by herbivorous animals. (1) The large size and considerable weight 

 of the projectile is advantageous in that it permits of the projectile 

 being cast away by a relatively large and powerful gun and receiving 

 from the gun sufficient momentum to carry it against the resistance 

 of the air and by a parabolic trajectory to the grass and other herbage 

 surrounding the dung on which the fruit-body has developed. 

 (2) The great violence of projectile-discharge ensures that the pro- 

 jectile will be shot clear of the dung on which the fruit-bodies grow 



1 H. Rehm, in Rabenhorst's Kryptogamen- Flora von Deutschland, Oeslerrehh 

 urul der Schweiz, Aufi. II, Bd. I, Abteil. 3, 1896, p. 1127. At Winnipeg, Ascobolus 

 immersus occurs commonly on fresh horse dung kept moist for about a month in the 

 laboratory. 



