i8 



BACTERIA, YEASTS, AND MOLDS 



considerable number of them are seen together they have 

 a bluish tinge. The spore-bearing branches spring up in 

 thousands all over the mold, and after a few days its sur- 

 face is covered with a mass of thousands of spores, giving 

 to the mold first a slightly blue color and later a darker 



blue, until the entire sur- 

 face finally becomes cov- 

 ered with the well-known 

 shade spoken of as blue 

 mold. These 

 spores are ex- 

 tremely light, 

 are very easily 

 blown by the 

 winds and readi- 

 ly float in the air. 

 Every breath of 

 air striking a 

 mass of molds 

 in full fruit will 

 detach some of these minute spores and blow them away. 

 The species of different molds can easily be distinguished 

 by their different modes of forming spores. A mold com- 

 mon on fruit and bread, called Miicor (Fig. 2), produces 

 its spores inside of little sacs borne on long stalks. The 

 mycelium in this mold is coarse and the threads are easily 

 visible, making a loose mass of delicate fibers, and some- 

 times forming upon bread a fluffy growth an inch thick 

 (Fig. 2). When ready to fruit, threads grow vertically 

 into the air and the end of each thread soon swells into a 

 small rounded knob. This knob continues to grow until 



Fig. 7. A colony of Mucor, showing the mycelium 

 and the sporangium of the fruit capsules. At a 

 is a large sporangium filled with spores. 



