THE PILOBOLUS GUN AND ITS PROJECTILE 69 



elongated), a cylindrical stipe, a large 

 pear-shaped subsporangial swelling, and a 

 columella which is surrounded and hidden 

 from external view by the sporangium 

 (Fig. 27). The sporangium is a black 

 discoid body filled with thousands of 

 orange-yellow oval spores. 



A fruit-body of Pilobolus Kleinii, which 

 was of typical form, full-grown, and just 

 about to shoot away its sporangium, was 

 placed on a slide in water under a raised 

 cover-glass, and its upper part was care- 

 fully drawn with the camera lucida. With 

 the help of this drawing, a median ver- 

 tical section of the upper part of a typical 

 fruit-body was constructed semi-diagram- 

 matically, and the drawing which resulted 

 is reproduced in Fig. 28. 



As shown in Fig. 27, the basal swell- 

 ing, the stipe, the subsporangial swelling, 



Fig. 27. — Pilobolus Kleinii. Diagram of an optical 

 longitudinal section of a living fruit-body, togetlier 

 with part of the mycelium to which the fruit- 

 body is attached in the substratum. The sub- 

 stratum (dung, dung-agar, etc.), s. The my- 

 celium : a-6, a main hypha from which the fruit- 

 body originated ; c c, thinner secondary hyphae, 

 branches of the main hypha ; d, an apophysis 

 (swelling on the main hyplia), separated from the 

 fruit-body by a septum. The fruit-body consists 

 of a unicellular sporangiophore e, f, g, h and of a 

 sporangium ni, )i, o. The sporangiophore : e, the 

 basal swelling ; /, the cylindrical stipe ; (j, the 

 pyriform subsporangial swelling ; h, the columella ; 

 i, the great vacuole of the sporangiophore filled 

 with clear cell-sap ; _/, drops of clear mucilaginous 

 licjuid excreted from the sporangiophore and spor- 

 angium ; k, a red, carotin-containing, biconcave, 

 perforate, protoplasmic septum at the top of the 

 stipe ; /, a shallow reddish ring of protoplasm 

 at the top of the subsporangial swelling. The 

 sporangium : 7U, the black sporangial wall ; )i, 

 colourless jelly situated in the lower part of 

 the sporangium between the spore-mass and 

 the wall of the sporangium and columella ; o, 

 numerous oval orange-yellow spores. Magnifica- 

 tion, about 23. 



c 



o 



o 



