CLASSES OF PLANTS 



433 



3. Basidiomycetes (fungi bearing spores in open). Most of 

 the common toadstools and mushrooms are in this group, includ- 

 ing the ones most widely used for food. There is no general dis- 

 tinction between edible mushrooms and poisonous ones ; very 

 often both kinds are found in the same genus. While it is 

 dangerous to take any chances with forms that are not well 

 known to be fit to eat, 

 it is not difficult to 

 learn to know the dif- 

 ferent species apart. 

 Rusts and smuts are 

 among the most de- 

 structive fungi and 

 may ruin a whole sea- 

 son's crop in a short 

 period. The various 

 forms of bracket, or 

 shelf, fungus usually 

 live on dead trees 

 but may be destruc- 

 tive to cut timber. 

 The brown, fluffy pulp 

 of these fungi is some- 

 times made into the 

 punk which will hold 

 a spark for a long 



time without bursting into flame. It is sometimes used in in- 

 cense sticks and as an absorbent in fine dental work. It was 

 formerly used as a tindier before matches became so common. 



320. Lichens. These curious partnerships between a fungus 

 and an alga are found in all parts of the world. They probably 

 play an important part in converting rock into soil. Iceland 

 moss and reindeer moss serve as fodder for reindeer. 



321. Mosses and ferns. The peat moss {Sphagnum) fills up 

 bogs and swamps, gradually decays, and becomes converted into 

 peat (see page 419). It can absorb much water and has been 



Fig. 178. Yeast plant 



The cells of this plant multiply by pushing out buds. 

 Under certain conditions the protoplasm of a cell 

 divides into two and then four parts, which then can 

 remain inactive for an indefinite time. These resting 

 cells are called spores 



