392 PLANT DISEASES 



Alcohol dissolves out of any part of the fungus a yellow- 

 brown colouring matter. 



Polyporus betulinus, Fries, Sysf. Myc., i. p. 358. Pileus 

 8-15 cm. across, thick, corky, elastic, hoof-shaped, sessile, 

 obliquely umbonate behind at the point of attachment, 

 margin obtuse, incurved, sterile, pileus covered with a 

 thin, greyish, brownish, or whitish crust which peels off, 

 exposing the white flesh, zoneless, glabrous ; pores up to 

 ^ cm. long, pores minute, unequal, whitish ; spores white. 



Polyporus borealis, Fries, Sysf. Myc., i. p. 366. Hori- 

 zontal, subspathulate, or reniform, either narrowed behind 

 into a short, more or less distinct stem, or thick and sessile, 

 4-8 cm. broad, whitish, then dingy yellow, spongy, then 

 corky, compact, hairy, often radiately rugose, rigid and 

 incurved when dry ; flesh thick, whitish, formed of parallel 

 fibres ; tubes 4-8 mm. long, pores unequal, white, dis- 

 sepiments thin, torn ; spores colourless, subglobose, 4 /* 

 diam. ; inodorous when fresh, but with a slight spicy smell 

 when dry. 



Fomes, Fries. Pileus hard and woody from the first, 

 flesh composed of interwoven hyphae, covered with a hard, 

 crustaceous cuticle, not zoned but often concentrically 

 grooved; perennial, forming successive strata of tubes, 

 the last formed and external layer of pores only living. 



Fomes fomentarius, Fries, Sysf. Myc., i. p. 374. Hoof- 

 shaped, 10-20 cm. across, 8-15 cm. thick at the base, 

 distantly concentrically sulcate, glabrous, opaque, fuliginous 

 or dingy brown, cuticle thick, hard, persistent, margin at 

 first with a white bloom, then ferruginous; flesh rather 

 soft, compactly floccose, foxy rust-colour ; tubes very long, 

 2-6 cm. long, distinctly stratose, ferruginous, pores sub- 



