FUNGI 



38s 



they produce. (See Fig- 

 ure i'/5-) These Ught, 

 powdery spores are scat- 

 tered by currents of air. 

 Bread mold, like some 

 other of the simpler fungi, 

 has a sex method of re- 

 production. Under right 

 conditions, special hyphas 

 appear whose tips come 

 together in pairs. These 

 are the sex branches. 

 (See Figure 184.) The 

 hyphse of bread mold, 



Fig. 182. — A bracket fungus growing on a 

 linden tree. — AJier Andrews. 



like the filaments of Vaticheria, are not divided by cross 

 walls, but a cross wall appears behind the tip of the sex 

 branches. In this way a protoplast is cut ofif from the rest 

 of the body. After the tips of two sex branches have 

 come in contact, the walls are absorbed, and the two proto- 

 plasts fuse. Evidently these protoplasts are gametes and 

 the result of their fusion is an oospore. This oospore turns 

 black. It forms a heavy wall about itself. It is capable 

 of surviving under conditions which would cause the death 

 of the spores of the sporophore. 



c. Mildews. — If you have ever noticed the leaves of 

 lilac bushes you have probably noticed that some of them 

 often seem dusty. This dusty appearance is due to a 

 parasitic fungus which grows upon them. It is the lilac 

 mildew. Many parasitic fungi grow within the tissues 

 of their host, only the sporophores growing up to the sur- 

 face; but this one spreads its mycelium over the surface 

 of its host, only the haustoria growing down into its tissues. 



