464 



FUNGOUS DISEASES OF PLANTS 



white, with little or no stipe, yellowish green pores, and spores 

 7-8 x 3^/4. 



Polyporus Betulinus (Bull.) Fr. is the cause of a sapwood decay 

 in several species of birch, and it is very widely distributed. 



Polyporus Fraxinophilus Pk., a rather small white form with 

 pileus 5-10 x 2.5-4 cm., produces an important disease in the 

 white ash (Fraxinus americana). 1 



IX. FOMES 



ATKINSON, GEO. F. Studies of Some Shade Tree and Timber Destroying 

 Fungi. Cornell Agl. Exp. Sta. Built. 193 : 199-235. Jigs. 5 6-94. 1901. 



SCHRENK, H. VON. Diseases of Deciduous Forest Trees. Bur. Plant Ind., 

 U. S. Dept. Agl. Built. 149 : 1-85. ph. i-io. 1909. 



The genus Fomes includes 

 among its representatives the 

 most destructive forest-tree 

 organisms in this order of 

 fungi. The conspicuous 

 bracket-like and hoof-shaped 

 sporophores are familiar to 

 all who have given the typ- 

 ical, temperate moist forests 

 any attention. They are, for 

 the most part, moisture- 

 loving, wound fungi ; and, 

 consequently, they find in the 

 conditions of the forest the 

 opportunity for their maxi- 

 mum destructiveness. They 

 may be entirely absent from 

 shade and meadow trees. 

 Among many species of com- 

 mon occurrence, special 

 mention should be made of 

 Fomes igniarius, Fomes 

 fomentarius, and Fomes Pi- 

 nicola. Fomes applanatus is 



FlG. 230. /''M//-.V FOMENTARIUS ON DEAD 



J'.i.i.c H. (Photograph by Geo. F. Atkinson) 



1 Schrenk, II. von. Bur. Plant Ind., U. S. Dept. Agl. Built. 32 : 1-18. ph. 1-5. 1903. 



