DEVELOPMENT OF PLANTS 259 



other corn plants by means of their basidiospores (Fig. 167, B). 

 In other cases, the teliospores germinate in the spring, infesting 

 the seedlings. This appears to be always the case in the de- 

 structive wheat, rye, oat 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 coppeP" 

 sulphate. _^^- — " 



97. Order c. Agaricales or Mushrooms and Toadstools.—^ 

 This is the most familiar group of the basidiomycetes and its 

 12,000 odd species are commonly 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 

 thrive 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. 168). 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. 

 In certain species the mycelium is phosphorescent and the cause 

 of the pale light that sometimes appears upon moist decaying 

 wood, the so-called fox wood. The mycelium bears at various 

 places the complex fleshy or woody body commonly known as 

 the mushroom or toadstool. If the mycelium grows in a regular 

 manner, radiating outward in all directions, then the mushrooms 

 will have a similar arrangement. The older central portions of 

 the mycelium will finally die off, while the newer portions con- 

 tinue to radiate outward and produce the mushrooms, which con- 



