FUNGI 



181 



318. Spores of nracor 

 some germinating. 



Mould. One of these moulds, Mucor mucedo, which is very com- 

 mon on all decaying fruits and vegetables, is shown in Fig. 317, some- 

 what magnified. When fruiting, this mould appears as a dense mass 

 of long white hairs, often over an inch high, standing erect from the 

 fruit or vegetable upon which it is growing. 



The life of this mucor begins with a minute 

 rounded spore (a, Fig. 318), which lodges on the 

 decaying material. When the spore germinates, 

 it sends out a delicate thread which grows rapidly 

 in length and forms very many branches which 

 soon permeate every part of the substance on which 

 the plant grows (b, Fig. 318). One of these threads is termed a hypha. 

 All the threads together form the mycelium of the fungus (180). The 

 mycelium disorganizes the material in which it grows, and thus nour- 

 ishes the mucor plant (Fig. 317.). It corresponds physiologically to 

 the roots and stems of other plants. 



When the mycelium is about two days old it begins to form the 

 long fruiting stalks which we first noticed. To study them, use a 

 compound microscope magnifying about two hundred diameters. One 

 of the stalks, magnified, is shown in Fig. 319, a. It consists of a 

 rounded head, the sporangium, sp, supported on a long, delicate stalk, 

 the sporangiophore, st. The stalk is separated from the sporangium 

 by a wall which is formed at the base of the sporangium. This wall, 

 however, does not extend straight across 

 the thread, but it arches up into the spor- 

 angium like an inverted pear. It is known 

 as the columella, c. When the sporangium 

 is placed in water, the wall immediately 

 dissolves and allows hundreds of spores, 

 which were formed in the cavity within 

 the sporangium, to escape, &. All that is 

 left of the fruit is the stalk, with the pear- 

 shaped columella at its summit, c. The 

 spores which have been set free by the 

 breaking of the sporangium wall are now 

 scattered by the wind and other agents. 

 Those which lodge in favorable places be- 

 gin to grow immediately and reproduce 

 the fungus. The others soon perish. 



The mucor may continue to reproduce itself in this way indefi- 

 nitely, but these spores are very delicate and usually die if they do not 

 fall on favorable ground, so that the fungus is provided with another 



319. Mucor. a, sporangium; 



b, sporangium bursting; 



c, columella. 



