340 



PHYSIOLOGY OF THE FUNGI 



Fig. 69. A, a median longitudinal section of Pilobolus kleinii just before discharge oi 

 sporangium. The gun is pointed at an acute angle away from the light source. The 

 light rays that strike the sporangium are screened out. The rays that strike the side of 

 the subsporangial swelling are bent and concentrated on the oposite side. This presum- 

 ably gives a photochemical stimulus which is conducted to the motor region below the 



