252 TEXT-BOOK OF FUNGI 



replete with spores alight on growing grass surrounding the 

 dung, and become fixed there by a viscid substance that is 

 insoluble in water after it has been exposed to the air. If 

 grass bearing such sporangia is eaten by some herbivorous 

 animal, the spores pass uninjured through the alimentary 

 canal, and produce a crop of the fungus on the dung. By 

 this method the fungus is distributed, and it may probably 

 be thus introduced to new countries on hay. 



Mucorineae 



Mycelium not anastomosing; sporangia polysporous, 

 furnished with a columella and a homogeneous wall. 

 Some species, as Mucor, form a copious vegetative my- 

 celium, which spreads in the substratum. In other forms, 

 as Rhizopus and Circinella, the vegetative mycelium is 

 scanty. Characters of systematic importance are afforded 

 by the sexual branches, which may be curved or straight, 

 smooth or spinulose, etc. In some genera, as Mucor, 

 Phycomyces, Spinellus, and Sporodinia, the progametes are 

 of equal size, whereas in Helicostylum, Thamnidium, Rhizo- 

 pus, and Circinella, the two progametes are unequal in 

 size. In many species zygospores are rare, and in not 

 a few forms, altogether unknown. In Circinella the 

 branches bearing the sporangia are strongly recurved, and 

 the sporangia dehisce in a circumscissile manner at the 

 centre, the basal half persisting. 



Many species are parasitic on decaying vegetable or 



5, optical section of a sporangium : a, columella : b, sporangial sac filled 

 with spores (technically conidia) ; 6, spores from sporangium, some germi- 

 nating ; 7, spores on a larger scale to show markings on epispore ; 8, 

 mature zygospore, the suspensors are indicated ; 9, mycelium running be- 

 tween cells of bulb containing starch. Figs, i and 2, nat. size ; rest mag. 



