THE PILOBOLUS GUN AND ITS PROJECTILE 159 



its apex (Figs. 77, C, and 78, B) or in some intermediate position. 

 I have observed that two sporangia which had landed upside-down 

 had lost their gelatinous ring (Figs. 77, C, and 78, B). It seems 

 likely that the loss of this wettable substance was the cause of the 

 sporangia coming to rest upside-down. The sporangium which 

 had landed in such a way as to rest on its side (Figs. 77, B, and 78, A) 



Fig. 78. — Pilobolus longipen. Two projectiles which landed on a glas.s glide abnor- 

 mally ; seen from above under the low power of the microscope. A, the sporangium 

 is resting on its side : a, the sporangium -wall ; b, spores, outside the 

 sporangium ; c, the gelatinous ring, abnormally torn and displaced ; d, pre- 

 cipitate from the drop of sap which accompanied the sporangium. B, the 

 sporangium is resting upside down ; it lacks its gelatinous ring : a, the 

 sporangium-wall incurved over the spores ; b, spores inside tlie sporangium ; 

 c, the columella through which spores can be seen ; d, precipitate of crystals 

 and amorphous particles from the drop of sap which accompanied the 

 sporangium ; e, the surface of the glass slide. Magnification, lUU. 



had its gelatinous ring broken and displaced. Here, again, the 

 abnormal position taken up by the sporangium appears to have 

 been caused by an accident to the gelatinous ring, in this case its 

 displacement from its usual position. 



It has been shown (1) that the sporangium alights on any object 

 it strikes so that its gelatinous side is turned toward the object 

 struck and (2) that the ring of jelly, on drying up, attaches the 

 sporangium to its substratum. We may now enquire into (3) the 

 effectiveness of the attachment after it has once been accomi)lished. 



