THE SPHAEROBOLUS GUN 



347 



the absence of light the mycelium of Sphaerobolus stellatus is unable 

 to form fruit-bodies, but that when once fruit-bodies have come 

 into existence and have advanced to a certain stage they can ripen 

 in the dark, although more slowly than in the light. If a culture 

 bearing fruit-bodies is placed 

 in a dark chamber, the more 

 mature fruit-bodies continue 

 to discharge their glebae for 

 many hours. This continu- 

 ance of glebal discharge in 

 the entire absence of illumina- 

 tion has been verified by 

 various observers, including 

 the writer. 



In unilateral light, the 

 fruit-bodies of Sjihaerobolus 

 stellatus and, doubtless, of all 

 species of Sphaerobolus 

 develop in such a way that : 

 when they open stellately, 

 their mouths face the incident 

 rays of light ; and, when they 

 discharge, their projectiles are 

 shot toward the source of the 

 light. I called attention to 

 these facts in 1920. x At the 

 time, Miss Walker was not 

 able to accept them ; but, in 

 1927, she 2 supported them 

 with observations of her own. 

 One of two experiments, made 



in my laboratory, which afford convincing evidence that light 

 influences the direction in which a fruit-body develops will now 

 be recorded. 



Fig. 165.- — Heliotropism of Sphaerobolus 

 stellatus. Fruit-bodies developing on 

 the top of a board which rested on the 

 floor of a large glass case. The black 

 arrows indicate the direction of the 

 incident light. Each fruit-body de- 

 veloped in such a way that its long 

 axis became parallel to the rays of light 

 and so that its apex came to face the 

 light. The fruit-body behind the white 

 arrow has just discharged its projectile 

 toward the source of maximum light, 

 and its everted double inner membrane 

 is now visible at its mouth. Board 

 found at Kenora, Ontario, Canada. 

 Natural size. 



1 At the Chicago meeting of the Botanical Society of America, held Dec. 20, 1920. 

 As it happened, Miss Walker and I read papers on Sphaerobolus in succession. 



2 L. B. Walker, 1927, he. cit., p. 159. 



