THE SPHAEROBOLUS GUN 299 



jectiles (the sporangium in Pilobolus, a mass of eight cohering 

 spores in the Ascobolus) are exposed to the sun whilst they are 

 attached to grass in pastures. 



The Structure and Mechanism of the Gun. — The glebal mass is 

 cast out of the Sphaerobolus gun by a catapult mechanism of great 



Fig. 148. — Sphaerobolus stellatus. Median vertical section 

 of a nearly mature sporocarp. The peridium consists 

 of six layers : no. 1, mycelial hyphae ; no. 2, a 

 gelatinous layer ; no. 3, a pseudoparenchymatous 

 layer ; no. 4, a layer of interwoven, largely tan- 

 gential hyphae ; no. 5, a palisade layer becoming 

 pseudoparenchymatous above ; and no. 6, a thin 

 layer of pseudoparenchyma surrounding the gleba, 

 g. Section prepared and photographed by Leva B. 

 Walker. Magnification, 46. 



beauty and efficiency. At first the whole fruit-body is a spherical 

 or somewhat oval ball firmly attached by its base to the substratum 1 



1 According to Pillay (loc. cit., pp. 198-204 and Figs. 1-3), so far as the origin of 

 a fruit-body of Sphaerobolus stellatus is concerned, there are three structures to be 

 considered : ( 1 ) a mycelial sheet or cord, which has an upper and a lower wall 

 (Rindenschichten), (2) a stroma which is rounded, oval, or irregular-sided and has 

 a wall of its own (Stromarinde), and (3) a rudimentary fruit-body (Anlage) which 

 eventually becomes differentiated into a peridium and a gleba. He states that the 

 stroma originates as a swelling in the middle region of a mycelial sheet or cord and 



