THE PILOBOLUS GUN AND ITS PROJFXTILE 133 



When the sporangiophore contracts during the discharge of the spor- 

 angium, the volume of the sporangiophore decreases to at least one- 

 half of what it was originally (c/. A and B in Fig. 62), with the result 



Fig. 62. — Pilobolus Klein it. Changes in the upper part of the sporangiophore 

 immediately after the sporangium has been shot away, represented somewhat 

 diagrammatically. A, a fruit-body just before discharge : a, the stipe ; 6, the 

 subsporangial sweUing, crowned above the upper broken hne by a dehisced 

 sporangium in wliicli, between tlie two parts of the sporangium-wall, can be 

 seen tlie swollen gelatinous ring and some of the spores ; the top part of the 

 wall of the subsporangial swelling between the two broken lines contracts at 

 the moment of discharge and becomes the lip or collar of the swelling shown at 

 c in B. B, the contracted sporangiophore a fraction of a second after the 

 sporangium and a jet of cell-sap have been shot away ; the jet broke up into 

 droplets of which the last is shown above the arrow '; a, the stipe, now contracted 

 and bent ; b, the subsporangial swelling, contracted to about one-half its 

 original volume and now showing the lip or collar c which appears dark owing 

 to crystals being present on its exterior ; at the mouth of the swelling is seen 

 a drop of cell-sap d which is growing in size owing to continued contraction of 

 the wall of the swelling and stipe. C, about half a minute after B ; the drop 

 has become much larger and has attained its maximum size. D, a minute or 

 two after C ; the drop is evaporating and has almost disappeared. E, a minute 

 or two after D ; the drop has disappeared and the stipe and swelling have 

 collapsed irregularly ; c, the lip or collar now slightly tilted. F and G, respec- 

 tively, an oblique and a top view of the upper half of a collapsed swelling ; 

 c, the lip or collar still rounded and comparatively rigid. Magnification, 38. 



that most of, or perhaps all of, the cell-sap held in the subsporangial 

 swelhng is shot out into the air. At the same tmie, something like 

 one-half of the cell-sap held in the basal swelhng and stipe is forced 

 upwards into the subsporangial swelling, so that the subsporangial 



