268 PLANT DISEASES 



In general the fungi reproduce by means of spores. 

 Spores are very tiny, usually single-celled, somewhat 

 spherical bodies often protected by a thick wall. They 

 may be scattered by wind, water, insects, or in other 

 ways just as seeds are distributed. Many of these 

 spores are so small that it would take 5000 of them 

 arranged side by side to make a line one inch long. 

 When this tiny spore is blown, or carried in some 

 other way, into unfavorable conditions, it is often 

 able to resist such unfavorable conditions, as cold or 

 dryness, until favorable conditions return. Then the 

 spore commences to grow. It swells up and sends out 

 a small protuberance which soon lengthens into a thread. 

 This thread is known as a hypha (plural, hyphce). The 

 hypha elongates rapidly and may soon begin to branch. 

 The branches grow and again branch so that in a short 

 time a dense network of threads, or hyphae, may be 

 built up. These threads are so constructed that they 

 are well fitted to absorb a large amount of material. 

 In form and power of absorption they are similar to the 

 root hairs of the flowering plants. The whole mass of 

 threads which is engaged in absorbing nutrient material 

 is known as a mycelium. The mycelium after growing 

 for some time may send up special threads, and on these 

 special threads the spores are again formed. 



The two important parts, therefore, of the fungous 

 plant are the mycelium and the spores. The spores 

 and mycelia may differ very widely in different 

 fungi, but all fungi have some sort of spore and some 

 sort of mycelium. Rust spores, smut spores, mold 

 spores, and spores of the blight are very different from 

 one another when seen under the microscope, but they 

 all produce in general the same results ; namely, they 



