THE FUNGI. 121 



in other particulars, seeming to be more nearly related to 

 these than to any other plants. 



Botanists are divided in opinion as to whether the Fungi 

 have developed independently from a common origin or 

 are a heterogeneous group that has resulted from the de- 

 generation of different chlorophyl-bearing plants. The 

 weight of authority seems to be in favor of the latter view. 

 So strong is the resemblance in the life history of many of 

 the Fungi to algal forms, that both are placed in the same 

 classes in some schemes of classification, the Fungi being 

 treated simply as degenerate forms of Algse. 



Vegetative reproduction occurs in several different 

 ways, which will be considered in connection with different 

 plants. Sexual reproduction is known in some families, 

 but in the majority of cases the propagation is by asexual 

 processes. Reproduction by parthenogenesis occurs in 

 some forms. These plants are remarkable for polymor- 

 phism, i.e., they occur in different forms at different stages 

 of their existence. Polymorphism greatly complicates the 

 difficulties of the study of the Fungi, especially in matters 

 of classification. Our knowledge of these plants is still 

 very incomplete, owing to the difficulties in the way of 

 their study and the immense number of forms. There 

 are six classes : 



CLASS I. THE CHYTRIDIE^E. 



CLASS II. THE SMUT FUNGI (Ustilaginece) . 



CLASS III. THE MOLDS AND MILDEWS (Phy corny cetes). 



CLASS IV. THE SAC FUNGI (Ascomycetes). 



CLASS V. THE RUSTS (JEcidiomycetes or Uredinece). 



CLASS VI. THE TOADSTOOLS AND THEIR ALLIES (Basi- 

 diomycetes) . 



CLASS I. The Chytridieae. These are very simple 

 organisms. Alternation of generations from gametophyte 

 to sporophyte is known in some forms. Asexual repro- 



