DISPEESAL BY EXPULSIVE MECHANISMS. 



825 



trates into the body-cavity, and there it divides up repeatedly, forming numerous 

 cells throughout the body. The infected fly, sickening under the injurious influence 

 of the Fungus and almost at the point of death, seeks for some quiet spot in which 

 to die. It frequently chooses for its last resting-place a window pane, in which 

 case it is possible to thoroughly investigate the further development of the Fungus, 

 After the death of the fly the round cells of the Empusa, hitherto hidden in the 

 body-cavity, grow out into long tubes which pierce the skin of the fly's corpse and 

 appear as short club-shaped structures on the surface. A single egg-shaped conidium 



Fig. 456. — Distribution of spores by expulsive mechanisms. 



i Pilobolus cHstallinus before the sporaQgium breaks away. 2 xhe same at the moment when the sporangium is thrown 

 off. 3 Sporangium of Nepkrodium Filix-mas closed. * and ^ The same in the act of splitting and scattering the spores. 

 6 Sphcerobolus stellatus at the moment when the balls filled with spores are thrown off. '^ Peziza aurantia. 8 Longi- 

 tudinal section through this Peziza. The spores are escaping from two of the asci. All the figures magnified 



is then cut off" from each club-like end of the tube, and this is thrown off" in exactly 

 the same way as the sporangium of Pilobolus (cf. fig! 383 '', p. 672). Here, too, a 

 place is formed for the splitting, and here again the mucilaginous contents are 

 thrown off simultaneously with the conidium by the sudden contraction of the club- 

 shaped end of the tube, and the conidium is thus always surrounded by a gelatinous 

 adhesive mass (fig. 383 *). The distance of the projection may be as much as 2-3 cm., 

 which, considering the extraordinary minuteness of the conidia, is proof of great 

 power. The dead fly then appears to be surrounded by a veritable halo of detached 

 conidia which are firmly attached to the substratum (fig. 383 ^). This is to be accounted 

 for by the fact that, as( already stated, a part of the sticky mucilaginous contents of 

 the club-shaped end of the tube are thrown out with the conidia. This serves as 

 an adhesive material, and causes the conidia to adhere particularly firmly to glass 

 window panes. If a living fly which happens to be near is struck by the projected 



