THE SPHAEROBOLUS GUN 329 



laboratory and which had a projectile distinctly under the average 

 size, was inclined at an angle of about 45° to a horizontal plane. 

 The projectile, upon being discharged, struck the horizontal sheet 

 of tissue-paper at a distance of 11 feet 10-5 inches from the fungus 

 gun which had discharged it. 



It thus appears, from direct observation on fruit-bodies of S. 

 stellatus growing on a board of Kenora origin, that the Sphaerobolus 

 gun can fire its projectile about 7 feet 9 inches vertically upwards into 

 the air and, when inclined at an angle of 45°, about 15 feet horizontally. 

 Thus, as one would expect from the theory of ballistics (cf. Fig. 163), 

 the horizontal range of the gun is about twice the vertical range. 

 The range of the Sphaerobolus gun is astonishingly great when one 

 remembers that the diameter of the gun scarcely exceeds 2 mm. and 

 the diameter of the projectile scarcely 1 mm. 



Miss Walker's Observations on the Range of Various Sphaero- 

 boli. — Miss Walker, 1 working at the University of Nebraska at the 

 same time as myself, but independently, investigated the range of 

 the gun of three forms of Sphaerobolus : S. stellatus, S. stellatus var. 

 giganteus, and S. iowensis. She noticed that in her cultures, when 

 discharge took place, the projectiles were hurled to the top of the 

 flasks and that they struck there with such force that they made a 

 click loud enough to attract the attention of persons in an adjoining 

 room. She therefore decided to determine the height to which the 

 projectiles could be shot vertically upwards. She grew the fungi 

 in pure cultures on dung so that the fruit-bodies developed on the 

 horizontal upper surface of the medium and looked more or less 

 upwards (Fig. 142, p. 288). 



In her first attempt at finding the vertical range of the Sphaero- 

 bolus stellatus gun, Miss Walker set her culture at the base of a large 

 glass museum jar which was 7 feet high ; but the tube was not high 

 enough, as many of the glebal masses were shot to its top. 



With sheet-celluloid Miss Walker then constructed a long 

 cylinder about 5 metres high and 23 cm. in diameter and closed at 



1 L. B. Walker, " The Forceful Ejection of the Glebal Mass by Sphaerobolus," 

 Publications of the Nebraska Academy of Science, Vol. X, 1922, pp. 23-25; also " The 

 Development and Mechanism of the Discharge in Sphaerobolus iowensis and S. 

 stellatus,'" 1927, loc. cit., pp. 157-159. 



