188 



STUDIES IN CRYPTOGAMS 



345. Spores of mucor; 

 some germinating. 



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

 mon on all decaying fruits and vegetables, is shown in Fig. 344, 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. 345), 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. 345.) One of these threads is termed a hypha. All 

 the threads together from the mycelium of the fungus (194). The 

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

 ishes the mucor plant. (Fig. 344.) 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. 346, 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, how- 

 ever, does not extend straight across the 

 thread, but it arches up into the sporangium 

 like an inverted pear. It is known as the 

 columella, c. When the sporangium is placed 

 in water, the wall immediately ruptures and 

 allows hundred of spores, which were formed 

 in the cavity within the sporangium, to 

 escape, b. 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 favor- 

 able places begin 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 

 means of carrying itself over unfavorable seasons, as winter. This is 



ucor. a, sporangium; 

 b, sporangium bursting; 

 s, columella. 



