OUR COMMON MOULDS. 



403 



is one of the few moulds which grow on oil or oily substances, and is so 

 filthy in its habits as to flourish in the sewers and cesspools of cities. 

 It is so much like Fig. 2 in structure and manner of fruiting, though 

 many times larger, that it must pass without an illustration. 



The pulp of oranges is an especially favorable diet for some of the 

 most delicate moulds. A culture made of it will show decided signs 

 of mouldiness in twenty-four hours, and after thirty-six hours of growth 

 there is a fine crop for study. Those which we have seen on the bread 

 are invariably the first to appear here, though followed in a short time 

 by others, one of the most common of which is given in Fig. 5. At 

 the base a are some mycelial threads which penetrate the tissue of 

 the pulp, and from them, as they come to the surface, arise the fruit- 

 stalks which branch near the top into a loose head with the spore cap- 

 sules borne on the ends of the branches. At c is one of the Sporangia 

 more highly magnified, showing the spores to be larger and few in 

 number as compared with the Mueor. This species is a member of 

 the same family with those already mentioned, and has its similar zy- 

 gaspores. 



Fig. 5. 



Fig. (i. 



Corn-starch pudding, when placed in a bell-jar, remained unchanged 

 until the fourth week, when its surface became coated with a peculiar 

 yellow-colored substance, and a day or so after black specks began to 

 appear. When viewed with the microscope, this mould exhibited the 

 structure seen in Fig. 6. There arises from the unbranched and im- 

 bedded filaments a very much swollen end (a and b) filled with proto- 

 plasm, yellow globules of oil, and crystals (d). As this end increases in 

 size, a conti-action takes place near the upper end, and soon a distinct 

 spore capsule is formed of the end thus separated. When the plant is 

 ripe a black elastic coat covers the spore-case, which slips partly off 

 when the spores are discharged from below. There are several spe- 



