240 THE MYCELIUM OF THE AGARICALES 



without producing serious damage until the flowers appear, when 

 the mycehum increases greatly in the afifected ears and "tassels" 

 producing sometimes enormous malformation, especially in the 

 ears, which appear as glistening white blisters or pustules. Later, 

 these bodies change to a sooty black, owing to the transformation 

 of the cells of the mycelium (Fig. 164, A) into black greasy spores. 

 These spores are scattered in clouds upon the breaking of the 

 pustules and germinate much after the manner of the telio- 

 spores of the rusts, infesting the young and delicate parts of 

 other corn plants by means of their basidiospores (Fig. 164, B). 

 In other cases, the teliospores germinate in the spring, infest- 

 ing the seedlings. This appears to be always the case in the 

 destructive wheat, rye, oats and barley smuts. Infection only 

 takes place when the spores come in contact with the seed. Con- 

 sequently, in these cases, the fungus can more readily be fought 

 by treating the seed with some fungicide as formaline and copper 

 sulphate. 



96. Order c. Agaricales or Mushrooms and Toadstools. — 

 This is the most familiar group of the basidiomycetes and its 

 12,000 odd species are cortimonly referred to as mushrooms and 

 toadstools. These fungi are largely saprophytes, living upon 

 the humus in the soil and upon decaying wood. Several of the 

 genera are exceedingly destructive to trees and cause great loss 

 to the lumber industry. In the majority of cases, the fungi 

 appear unable to attack the living portion of the trees and only 

 thrives upon dead tissues, as the heart wood, which they quickly 

 disorganize and render worthless. As in all the preceding groups 

 of fungi, the real plant body is a delicate mycelium that spreads 

 through the soil or decaying substances, as may readily be dem- 

 onstrated by splitting open a tree infested with one of the fungi 

 (Fig. 165). The "spawn" that is sold in seed stores for plant- 

 ing in mushroom beds is a dried mass of decaying leaves and 

 straw mixed with earth, in which the mycelium of the mushroom 

 has been allowed to grow. Often the hyphae of the mycelium 

 lose their delicate character and become woven together, forming 

 rather dense woody strands or plates, a development frequently 

 seen in the timbers of mines and under the bark of decaying trees. 



