32 ELEMENTARY BIOLOGY. [V, 



transverse septa are formed between the masses thus divided 

 off from one another. But neither in this, nor in any other 

 Fungus, are septa formed in the direction of the length of 

 the hypha. 



Very early in the course of the development of the 

 mycelium, branches of the hyphse extend downwards into the 

 medium on which the mycelium grows ; while, as soon as the 

 patch has attained a certain size, the hyphse in its centre 

 give off vertical aerial branches, and the development of 

 these goes on, extending from the centre to the periphery. 

 The outgrowth of pencil-like bunches of branches at the end 

 of these takes place in the same order ; and these branches, 

 becoming transversely constricted as fast as they are formed, 

 break up into conidia, which are ready to go through the 

 same course of development. 



The conidia may be kept for a very long time in the dry 

 state, without their readiness to germinate being in any way 

 impaired, and their extreme minuteness and levity enable 

 them to be dispersed and carried about by the slightest 

 currents of air. The persistence of their vitality is subject 

 to nearly the same conditions of temperature as that of yeast. 

 Not unfrequently Torulce make their appearance, in abun- 

 dance, among the hyphse and conidia of Penicillium, and 

 appear to be derived from them ; but it is still a disputed 

 point, whether they are so or not. 



If some fresh horse-dung be placed in a jar and kept 

 moderately warm, its surface will, in two or three days, be 

 covered with white cottony filaments, many of which rise 

 vertically into the air, and end in rounded heads, so that 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 



