V.] MOULDS. 33 



their hyphae cross one another, interlace, and give rise 

 to a papyraceous crust. After the hyphas have attained a 

 certain length, the protoplasm divides at intervals, and 

 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 hyphae extend downwards into 

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

 as the patch has attained a certain size, the hyphae in its 

 centre give off vertical aerial branches, and the develop- 

 ment 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 Torulcz make their appearance, 

 in abundance, among the hyphae 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 



M. 3 



