252 



THE LOWER FUNGI— PHYCOMYCETES 



and light colored; the mature sporangium discharged with 

 violence from the end of the sporangiophore, commonly projected 

 for several feet, the columella being carried away with it; zygo- 

 spore formed at the point of union of conjugating branches which 

 lie in such a position as to give the appearance of a pair of tongs. 

 The genus contains a dozen or more species. It is particularly 

 interesting on account of the phenomenon of sporangial discharge 

 which anticipates conditions in the following order, where such 

 a discharge commonly occurs. An entertaining discussion of 

 the mechanism which accomplishes discharge is given by Buller 



Fig. 88. — Pilobolus crystallinus (Wiggers) Tode. (a) Sporangiophore, sub- 

 sporangial vesicle and sporangium, (b-d) Stages in zygospore formation. 

 (After Zopf 1888.) 



(1921). He finds that the neck of the subsporangial vesicle 

 ruptures just beneath the sporangium, and that sudden contrac- 

 tion of the sporangiophore results in the squirting out of a jet of 

 cell sap on which the sporangium is carried through the air. His 

 experiments have demonstrated also that the vesicle functions as 

 an ocellus (simple eye), and directs the tip of the sporangiophore 

 toward the light in order that the sporangium may be discharged 

 out of the crevices of the substratum into the lighted open. 

 These fungi are found in nature on dung of herbivorous animals, 

 and the spores germinate only after passing through the alimen- 

 tary canal. The surface of the sporangial wall is adhesive. The 

 sporangium falling on the grass or other herbage, adheres, is later 

 eaten by the browsing animal, and enabled to complete its life 



