THE FUNGI WHICH CAUSE PLANT DISEASE 431 



On red cedar and arbor vitae causing pockets, also on dead 

 spruce and fir. The cellulose is almost all removed from the 

 affected cells of the heart wood. The mycelium is scant and when 

 young is pale and with numerous clamps. It extends horizontally 

 through the tracheids, giving off lateral branches. None is found 

 in the sap wood. 



F. annosus (Fr.) Cke."'"^ (=Trametes, radiciperda R. Hartig). 



Pileus woody, dimidiate, very irregular, conchate to applanate, 

 10-13 X 5-8 X 0.5-2 cm.; surface at first velvety, rugose, anoderm, 

 light brown, becoming thinly encrusted, zonate, and finally black 

 with age; margin pallid, acute, becoming thicker; context soft- 

 corky to woody, white, 0.3-0.5 cm. thick; tubes unevenly stratified, 

 2-8 mm. long each season, white, mouths subcircular to irregular, 

 3-4 to a nmi., edges rather thin, entire, firm, white, imchanging: 

 spores subglobose or ellipsoid, smooth, hyaline, 5-6 x 4-5 fi. 



On pine, fir and various deciduous trees, described by Hartig^* 

 as the most dangerous of all conifer parasites. It is not so plentiful 

 in America as in Europe. 



The sporophores appear near or on the roots, between the 

 bark scales, where the white felted delicate mycelium also occurs. 

 The spores, carried presumably by rodents, germinate upon the 

 bark of roots; the mycelium penetrates to the living cortex, forces 

 its way into the wood and follows up the stem and down the root. 

 The parenchyma cells are killed and browned; the wood becomes 

 violet, later brownish-yellow. The hyphsB travel in the cell- 

 lumen and pierce the walls. The lignified parts are dissolved 

 first, later the middle lamella disappears. Eventually the whole 

 root system may become involved and the death of the tree result. 



F. juniperinus (v. Sch.) S. & Sy.^ 



Pileus woody, ungulate, 3-5 x 5-8 x 5-7 cm. ; surface tomentose, 

 deeply sulcate, ferruginous to gray, at length rough and grayish- 

 black; margin obtuse, velvety, melleous or ferruginous to hoary: 

 context corky to woody, reddish-fulvous, 0.5-1 cm. thick; tubes 

 indistinctly stratified, 0.5-1 cm. long each season, melleous within, 

 reddish-fulvous in the older layers, mouths circular to angular, 

 2-3 to a mm., edges rather thin, entire, even, melleous: spores 

 reddish-brown, smooth; spines blunt, only slightly projecting. 

 On red cedar. 



