THE SPHAEROBOLUS GUN 333 



before it is about to discharge its projectile, it is possible to cause 

 the fruit-body to discharge its projectile at any moment with the 

 help of mechanical pressure exerted by means of a pin. In a fruit- 

 body about to discharge its projectile there is always a space between 

 the upper everting membranes and the lower non-everting mem- 

 branes except at the points of the teeth (Fig. 161, A and B, p. 316). 

 I found that, if one pushes the end of a pin down the sinus between 

 two teeth into the space just described so that the end of the pin 

 presses very slightly against the everting membranes, the everting 

 membranes at once turn inside out and shoot away the projectile 

 in a normal manner. 



Using a pin (shown at / in Fig. 164, B) in the manner just 

 described, I caused the four stellately-opened fruit-bodies shown at 

 d in Fig. 164, A, to discharge their projectiles. The same four 

 fruit-bodies after discharging their projectiles are shown at g in 

 Fig. 164, B : the everted membranes can now be seen as a pearly 

 dome covering each of the fruit-body mouths. 



The Horizontal Range of Sphaerobolus stellatus of Winnipeg 

 Origin. — In November, 1923, I found Sphaerobolus stellatus growing 

 on cow-dung plats in pastures at the Manitoba Agricultural College, 

 near Winnipeg. Some of the dung was taken to the laboratory and 

 kept moist in large crystallising dishes. Numerous fruit-bodies 

 soon developed on the surface of the dung (Fig. 164) and, about a 

 week after the dung had been collected, they began to discharge 

 their glebal masses. 



To determine approximately the horizontal range of the 

 Sphaerobolus guns which had developed on the cow dung my 

 procedure was as follows. Between 12 noon and 1 p.m. on Decem- 

 ber 23, 1923, when a number of fruit-bodies were about to discharge 

 their glebal masses, I removed a piece of dung (like that shown in 

 Fig. 164) from the culture dish, held it in my hand 2 feet 6 inches 

 above the floor of the laboratory and then, by means of the pin- 

 trigger method already described, caused a number of fungus guns 

 to discharge their projectiles in succession. Each gun was inclined 

 upwards at an angle of 45° or less from the horizontal and was so 

 directed that its projectile, on falling, would land on one or other of 

 some large sheets of white paper spread over a series of tables some 



