DEVELOPMENT OF PLANTS 



265 



production is characteristic of nearly all of the Agaricales and it 

 is not surprising that a bit'of dead wood or piece of lumber can 

 not be exposed without being infested with the spores. 



E. Boletaceae or Fleshy Pore Fungi. The members of this 

 family are generally characterized by a stalk and a pileus which 



FIG. 173. Pore forms of the Agaricales: A, Boletus, showing fleshy pore- 

 bearing layer, p. B, top view of a woody, bracket form, Elfvingia. The 

 concentric lines represent the annual growth. C, section of a similar form, 

 showing three layers of pores that represent three year's growth. D, en- 

 larged view of under surface, showing one of the pores with hymenial layer. 



bears pores, the latter being easily separable as a layer from the 

 pileus (Fig. 173, A). 



F. Agaricaceae or Gill Fungi. These fungi more commonly 

 assume an umbrella form, although some of them are of the 

 shelving bracket type (Fig. 170). The hymenium is arranged 

 on the surface of gills or plates. Many of them are highly 

 prized for the table, though they contain comparatively little 

 nourishment, and must be regarded as relishes rather than foods. 

 While the majority of the 5,000 species of the family are edible, 

 some of them contain the most deadly poisons. No rule can be 

 given that will enable the collector to separate these fungi into 

 the two mythical groups of poisonous toadstools and edible 

 mushrooms. Each species must be known individually before it 

 is safe to use them for food. All forms with a volva should be 

 most carefully identified, because this is a feature of the deadly 

 amanitas (Fig. 170), which are among the most poisonous plants 

 known. 



