DEVELOPMENT OF PLAN'IS 



227 



thick-walled gamctospore (Fig. 136, B, C). After a resting 

 period, this gametospore grows directly into a new mycelium. 

 In some of the black moulds Blakeslee has made known that 

 reproduction is only effected by the union of ]i\j)h;i(* frf)m 

 difTerent plants which must difTcr therefore in their nature, just 

 as you found to be the case in some species of Spirogyra. 



81. A Fly Fungus. — An interesting form allied to the nmcors 

 is seen in the parasitic fungus Empiisa, that produrcs an epi- 



FiG. 137. A fungus, Empusa, parasitic upon Hies: .1, lly surrounded hy 

 a mass of discharged sporangia. B, enlarged view of several h>phae, sh«>wing 

 the discharge of the sporangia which are surrounded by a mucilaginous sub- 

 stance. — After Brefeld. 



demic among flies at certain seasons when tlie\- may be m-cu dead 

 and clinging to the woodwork and window panes surroundeii by 

 a white halo (Fig. 137, A). This appearance is caused by the 

 discharge of numerous white sporangia that are found at the 

 ends of the hyphac that project from all sides of the fly's Ixxiy 

 (Fig. 137, B). If, In- chance, a i\y sliould rome within r.uigc 



