34 ELEMENTARY BIOLOGY. [CHAP. 



they somewhat resemble long pins. The organism thus 

 produced is another of the Fungi the mould termed Mucor 

 mucedo. 



Each rounded head is a sporangium ; the stalk on which 

 it is supported rises from one of the filaments which ramify 

 in the substance of the horse- dung, and are the hyphce. 

 Each hypha is, as in Penicillium, a tube provided with a 

 tough thickish structureless wall, which is partly composed 

 of cellulose, and is filled by a vacuolated protoplasm. In 

 old specimens, transverse partitions, continuous with the 

 walls of the hyphse, may divide them into chambers or cells. 

 The stalk of the sporangium is a hypha of the same structure 

 as the others. The wall of the sporangium is beset with 

 minute asperities composed of oxalate of lime, and it con- 

 tains a great number of minute oval bodies, the spores, held 

 together by a transparent intermediate substance. When the 

 sporangium is ripe, the slightest pressure causes its thin 

 and brittle coat to give way, and the spores are separated 

 by the expansion of the intermediate substance, which 

 readily swells up and finally dissolves, in water. The greater 

 part of the wall of the sporangium then disappears, but a 

 little collar, representing the remains of its basal part, 

 frequently adheres to the stalk. The cavity of the stalk 

 does not communicate with that of the sporangium, but is 

 separated from it by a partition, which bulges into the 

 cavity of the sporangium, forming a central pillar or pro- 

 jection. This is termed the columella and stands con- 

 spicuously above the collar, when the sporangium has burst 

 and the spores are evacuated. 



The spores are oval and consist of a sac. having the 

 same composition as the wall of the hypha, which encloses 

 a mass of protoplasm. When they are sown in an appro- 

 priate medium, as for example in Pasteur's solution, they 



