THE PILOBOLUS GUN AND ITS PROJECTILE 8i 



charged sporangium and examining the fragments under the 

 microscope. If one mounts a newly discharged moist sporangium 

 in water on a slide and then presses on the cover-glass so as to give 

 it a lateral movement, one can often separate the sporangium into 

 its component parts, namely : (1) the orange-yellow spores ; (2) the 

 intensely black, free, convex, cap-like portion of the sporangium- 

 wall ; (3) the annular mass of jelly ; and (4) the obtusely conical 

 wall of the columella, to the 

 rim of which is attached the 

 narrow band of sporangium- 

 wall (covered with fine par- 

 ticles) which separated from 

 the cap-like portion of the 

 sporangium-w^aU when the 

 wall, owing to pressure from 

 the annular mass of jelly, 

 was split transversely into 

 two parts. Photomicrographs 

 of columellae isolated in the 

 manner just described are 

 shown in Figs. 36 and 37. 



An examination of isolated 

 columellae in side view, like 

 that shown in Fig. 36, revealed 

 the fact that each columella 



Fig. 



37. — Pilobolus longipes. Photomicro- 

 graph of a columella and some isolated 

 spores obtained bj' rubbing a discharged 

 sporangium laterally in water under a 

 cover-glass. The columella is cap- 

 shaped : a, its central peak, here 

 flattened irregularly ; b, its brim ; and 

 c, its marginal band (part of the spor- 

 angialwall). Isolated spores, d. Mag- 

 nification, 105. 



is shaped like a cap and that, 



whereas the wall of the brim (6) is relatively thin, the wall of the 

 peak (a) is thick and apparently gelatinously swollen. There can 

 be but little doubt that, as a discharged projectile dries up and 

 the columella comes to press against the substratum, the wall of 

 the columella assists the annular mass of jelly in causing the spor- 

 angium to become adherent to the substratum. 



That the mass of jelly produced within a sporangium is truly in 

 the form of a hollow ring was established by dissection carried out 

 as follows. A ripe fruit-body of Pilobolus longipes was submerged in 

 a drop of water, and its sporangium was pulled away from the colu- 

 mella with the help of a needle. A cover-glass was then placed over 



VOL. VI. 



