132 



RESEARCHES ON FUNGI 



The Pilobolus gun, as pointed out in an earlier Section, ^ is 

 discharged explosively : the wall of the sporangiophore breaks 

 across transversely just beneath the sporangium and columella 

 [vide the dotted line a in Fig. 28, p. 70) ; the elastic wall of the 

 subsporangial swelling, stipe, and basal swelling, which has been 

 distended by the pressure of the cell-sap in the great vacuole, 

 suddenly contracts ; the cell-sap is violently squirted out of the 

 open mouth of the subsporangial swelling ; and a spherical drop of 



cell-sap carries away the sporangium 

 at a speed ^ of 10-20 feet per second 

 through the air. A contracted spor- 

 angiophore seen in water immediately 

 after the sporangium has been dis- 

 charged is shown in Fig. 61. 



In the process of squirting away the 

 sporangium, the subsporangial swelhng, 

 on account of its position just beneath 

 the sporangium, its large size, and the 

 great elasticity of its cell-wall, plays a 

 chief part. Its external appearance just 

 before the discharge of the sporangium, 

 immediately after, and during the next 

 few minutes, is illustrated in Fig. 62. 



The subsporangial swelhng, as may 

 be realised by a glance at Fig. 28 (p. 70), 

 contains a large amount of cell-sap. 



Fig. 61. — Pilobolus Kleinii. The sporangiophore 

 after the discharge of the sporangium ; seen 

 in water with the basal swelling embedded in 

 part of the substratum : s, the substratum ; 

 a b c, the sporangiophore, shrunken and 

 collapsed ; a, the basal swelling with a turgid 

 apophysis below ; b, the stipe ; c, the sub- 

 sporangial swelling with its open mouth to- 

 wards the observer ; and d, the contracted 

 collar of the subsporangial swelling now 

 forming a lip to the mouth of the swelling. 

 Upper half drawn with the help of the camera 

 lucida, the lower half somewhat diagram- 

 matic. Magnification, 53. 



1 Vide p. 62. 



2 Fide p. 67. 



