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PREFACE 



Polypores are tough or woody fungi found chiefly on wood in 



^* the form of brackets of various shapes and sizes, the fruiting 



surface being composed of tubes or furrows. Sometimes the 



* walls of these tubes split with age and the hymenium appears 

 spiny, resembling the hydnums; sometimes the furrows change 

 with age to appear like gills. When the fruit-body is perennial, 

 the tubes are often arranged in layers. The family may be 



^ divided into four groups, the resupinates, the annual poroid 



* species, the perennial poroid species, and the agaric-like species. 

 ^ The resupinate species cannot be satisfactorily studied without 



^J the advantages of a large herbarium and are therefore omitted 

 here, but some of the larger species of the other groups are com- 

 paratively easy. 



Polypores as a class are very destructive to trees and timber. 



*4. On the other hand, one species possesses medicinal properties, 



some of the encrusted species supply tinder, and several of the 



more juicy ones are excellent for food if collected when young. 



. The only species recognized as poisonous is the medicinal one, 



,j Fames Laricis, and it is so tough and bitter that no one would 



\ think of eating it. 



Jl Polypores are very easily collected and preserved and they 

 largely retain their characters when dried, which makes them 

 excellent objects for class study during the winter months. 

 Many of them, also, remain in situ during the winter in perfect 

 condition for collecting. As a group, they lend themselves 

 remarkably well to studies in gross and minute anatomy, vari- 

 ation, adaptation, and injurious effects on trees and structural 

 timbers. 



North America may be conveniently divided into five regions : 

 (i) eastern Canada and the northern United States southward 

 to the southern boundaries of Virginia, Kentucky, Missouri, and 

 Kansas, and westward to the western boundaries of Kansas, 

 Nebraska, and the Dakotas; (2) the southern United States, 



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