INTRODUCTION 



[CH. 



ascocarp, if present, 



either with no definite 



ostiole, or shield-shaped, 



or with asci irregularly 



arranged 



Plectomyietes 



1. Plectascales 



2. Erysiphales 



3. Exoascales 



ASCOMYCETES 



1 



ascocarp wide open 



when ripe ; asci in 



parallel rows 



Discomyeetes 



1. Pezizales 



2. Helvellales 



3. Phacidiales 



4. Hysteriales 



5. Tuberales 



ascocarp flask-shaped ; 



opening by an ostiole 



when ripe ; asci in 



parallel rows 



Pyrenovtycetes 



1. Hypocreales 



2. Dothideales 



3. Sphaeriales 



4. Laboulbeniales 



number of basidiospores 

 indefinite 



Hemibasidiomycetes 



I. Ustilaginales 



BASIDIOMYCETES 



number of basidiospores 

 definite, usually four 



SAPROPHYTISM, PARASITISM AND SYMBIOSIS 



Since fungi under no circumstances possess chlorophyll, they are neces- 

 sarily dependent for their food supply upon some sort of relation with another 

 organism. As saprophytes they may utilize organic storage materials 

 (sugar, etc.) or waste products, or may break up dead tissues as a source of 

 supply; as parasites they may prey upon living cells with consequences to 

 the host that vary from trifling inconvenience to complete destruction, or as 

 symbionts they may establish a relationship with another organism in 

 which the advantages are not wholly on one side. 



These various arrangements are connected by intermediate forms, and 

 by forms capable of parasitism or saprophytism according to circumstances. 

 A species which is strictly limited to one type of nutrition is an obligate 

 saprophyte, parasite, or symbiont, a species which is usually saprophytic 

 but capable of parasitic existence on occasion, is described as a hemi- 

 saprophyte or facultative parasite, and a form which is usually parasitic, 

 but sometimes saprophytic as a hemi-parasite, or facultative saprophyte. 



