THE PILOBOLUS GUN AND ITS PROJECTILE 149 



wall of the columella is attached, as shown in Figs. 35 (p. 79), 36 

 (p. 80), and 37 (p. 81), a very narrow circular collar-like band of the 

 sporangium-wall, which was separated from the convex cap-like 

 portion of the sporangium-wall when the pressure of the annular 

 mass of jelly caused the sporangium to dehisce. Within the 

 sporangium are enclosed many thousands of orange-yellow spores 



Fig. 73. — Pilobolus longipcs. The projectiles, eacli consisting of a spor- 

 angium and a large drop of cell-sap, were shot vertically upwards 

 for a distance of 4 feet 7 inches on to the under surface of a horizontal 

 glass plate. The drops then dried up and thus formed arovuid each 

 sporangiimi a white lialo of ])recipitated salts, etc. The photograph 

 is similar to tliat shown in Fig. 72, except that it was taken, not in 

 transmitted liglit, but against a black background in reflected ligiit. 

 Natural size. 



(Fig. 30, C). As we shall see shortly, the fate of the spores is in a 

 high degree dependent on the peculiar physical properties of the 

 membranes which bound the siDorangium at the moment of its 

 discharge. 



A Pilobolus projectile, as may be ascertained by examining it 

 immediately after it has struck a sheet of glass or paper, consists of 

 a sporangium and a large drop of cell-sap (Fig. 33, p. 77). When 

 the projectile strikes any object, e.g. a blade of grass, the drop of 

 cell-sap, owing to the force of impact, flattens out, and the sporan- 



