388 MOULDS AND YEASTS 



which usually appears in the substratum on which the 

 fungus is growing. For further details of its origin 

 and structure the student must refer to text-books of 

 mycology. 



(ii) Mucor pyriformis, Fischer, is another species 

 found on damp, bruised, and decaying apples and other 

 fruits, from the sugars of which it appears to be able to 

 produce small quantities of sweet-smelling esters and 

 citric acid. 



It possesses large brownish sporangia 350 to 400 /j, 

 in diameter, in which are oval spores 6 to 9 p long 

 and 4 to 5 /a broad : the columella is pear-shaped. 



(iii) Mucor racemosus, Fres., is a very widely dis- 

 tributed species upon fruit, bread, and vegetable tissues 

 of all kinds, and found also upon horse-dung, cheese, 

 and many dairy products. 



Its sporangia are small, from 20 to 60 ^ in diameter, 

 yellowish or brownish in tint, and borne 

 either upon simple unbranched hyphae 

 or on sporangiophores with short race- 

 mose branches (Fig. 55). 



The spores are smooth and elliptical, 

 5 to 6 & long and about 4 ^ broad ; the 

 columella is egg-shaped. 



The fungus grows best at 20 to 

 25 C, and is of especial interest on 

 account of its power of fermenting 

 FIG. $$. Mucor sugar solutions, with the production 



racemosus, Fres. ( X 5). -111 r i i i 



of considerable amounts of alcohol. 



This it largely accomplishes by means of sprouting 

 yeast-like cells which originate from submerged hyphae 

 or portions of the mycelium. 



Ex. 172. Place a piece of fresh horse-dung under a bell-jar 



