374 TEXT-BOOK OF FUNGI 



as weighing thirty pounds. Many species of Polyporus 

 often reach or sometimes exceed a foot in diameter, and 

 when perennial become very hard and woody. 



Some species of Polyporus are destructive wound-para- 

 sites, attacking trees. 



Among edible kinds may be enumerated several species 

 of Boletus, more especially B. edulis, also Fistulina hepatica. 

 Many species of Boletus are poisonous. 



In the majority the spores are minute, but in Boletus 

 they are exceptionally large, more or less spindle-shaped 

 and coloured. In Strobilomyces, a genus superficially 

 resembling Boletus^ the spores are globose, warted, and 

 coloured. 



Cystidia are present in abundance in some species of 

 Polyporus. 



The distribution of the family is cosmopolitan. The 

 majority grow on wood. 



Conidial forms have been described as present in cavities 

 in the young pileus of Fistulina hepatica by De Seynes. 

 The conidial forms of some species of Polyporus are pro- 

 duced on a body of considerable size preceding the forma- 

 tion of the sporophore. This conidial condition was at 

 one time accepted as a distinct genus of fungi called 

 Ptychogaster, 



GASTEROMYCETES 



The subterranean forms included in the Hymenogas- 

 traceae are almost universally considered as the most 

 primitive types, and starting-point of the present group; 

 but apart from the indehiscent nature of the protective 

 portion of the sporophore, called here a peridium, there 

 are no indications of morphological inferiority as compared 



