THE FUNGI : ARCHIMYCETES AND PHYCOMYCETES 243 



separates the body of the sporangium from the sporangiophore (Fig. 235). 

 The wall of the sporangium hardens and becomes brittle, and the entire 

 sporangium darkens in colour until it is almost black when mature. The 

 wall is covered with a deposit of small crystals of calcium oxalate. Not all 



Stalk 



Sporangium 



Columella 



Remains of 

 Sporangium wall 



Fig. 235. — Mucor miicedo. Asexual reproduction. A, Mature 

 sporangium before dehiscence. B, After dehiscence. C, Spores. 



species of Mucor produce terminal sporangia. In some they may be developed 

 on branched hyphae or in clusters. It is on such characters as these that the 

 species are chiefly separated. 



When mature the sporangium wall is surrounded by a drop of water, 

 secreted by the sporangiophore, and breaks round the base, leaving a ragged 

 collar attached to the sporangiophore. The spores are not immediately 

 shed but remain clinging together in a wet mass, and the means of their 

 dispersal is uncertain. It has been claimed that insects are the chief agents, 

 but it seems probable that eventually, when the whole mycelium has died 

 and dried up, that some spores at least are scattered in the air. Their wide 

 dispersal, especially in the soil, is otherwise difficult to understand (Fig. 234). 



Spores germinate immediately on reaching a suitable substratum and 

 produce a hypha from which a new mycelium develops. 



Sexual Reprouction 



It is well known that zygospores are only rarely found in cultures of 

 Mucor, but for long the reason for this was not understood. It was shown 

 by Blakeslee in 1904 that the mycelium of the Fungus is unisexual and not 

 capable of producing both male and female gametes. Sexual reproduction, 

 therefore, can only occur when diflFerent mycelia intermix. Two distinct 



