452 BASIDIOMYCETES. 



enough to cut through all roots, care being taken to leave no 

 diseased stems or roots outside the circle ; after remaining open 

 for a time, the ditch must be refilled with soU to prevent 

 development of sporophores on the exposed roots. Diseased stems 

 should be felled, and, along with all root-remains, burned on 

 the spot, where there is no risk of forest fire ; failing this, they 

 and their stumps should be deeply covered over with soil, to 

 prevent development of sporophores. 



The following species of Polyporus have been observed on 

 living trees, but details in regard to their parasitism and mode 

 of destruction are still wanting : 



P. officmalis Fr. On larch, chiefly in Russia, but also in France and 

 Switzerland. The sporophores are white irregular masses, and at one time 

 were used in medicine. The mycelium forms bands in the wood similar 

 to those of P. svlphweus. 



P. albus (Corda), according to Ludwig^ is a cause of a disease of Conifers, 

 ■which extends from the root upwards. (U.S. America.) 



P. spumeus (Sow.). On apple trees. (Britain and U.S. America.) 



P. fumosus (Pers.). On willow, ash, maple, and other broad-leaved trees. 

 (Britain and U.S. America.) 



P. picipes Fr. On willow and other broad-leaved trees. (Britain and 

 U.S. America.) 



P. (Fomes) cinnamomeus Frog. On cherry trees. (Britain.) 



P. radiatus (Sow.). On alder {A. incana), birch, and beech. (Britain and 

 U.S. America.) 



P. (Fomes) ribis (Fr.). On black currant and gooseberry shrubs. (Britain 

 and U.S. America.) 



P. (Polystictus) hirsutus Fr. (Britain and U.S. America). On living 

 hornbeam, alder, oak, birch, and service. A variety, scntposas, is common 

 and injurious on cherry. 



P. ulmarius Fr., is, according to Cavara,^ parasitic on living elm near 

 Pavia. (Britain and U.S. America.) 



P. (Fomes) nig^cans. On birch. (Britain and U.S. America.) 



P. salicinus (Pers.). A dangerous enemy of willow.^ (Britain and U.S. 

 America.) 



Rostrup'' gives Corticium comedens as a wound-parasite of oak and 

 alder. 



Hartig describes Fistulina hepatica, the liver-fungus, as causing a dark- 

 brown colour in oak-wood. 



^ Ludwig, Lehrbicch d. niederen Kryptogamen, 



-Cavara, Bevue Mycol., 1891. 



^Tursky, Russian translation of R. Hartig's " Lehrbuch d. Baumkrankheiten." 



■•Rostrup, Fortsatte Undersogdser, 1883. 



