FUNGI 



385 



Fig. 182. — A bracket fungus growing on a 

 linden tree. — After Andrews. 



they produce. (See Fig- 

 ure 175.) These light, 

 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 hyphee 

 appear whose tips come 

 together in pairs. These 

 are the sex branches. 

 (See Figure 184.) The 

 hyphse of bread mold, 

 like the filaments of Vaucheria, 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 off 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. 



