THE FUNGI WHICH CAUSE PLANT DISEASE 433 



This is a wound parasite on the heart wood of sassafras and is 

 also found on roots and stems of various shrubby plants including 

 rose, gooseberry and currant. The fungus fills the large vessels 

 and tracheids with a brown mycelium and dissolves the entire 

 wall locally. 



F. fulvus (Scop) Gill." 



Pileus woody, triquetrous, rarely ungulate, thick and broadly 

 attached behind, 1-3 x. 5-7 x 3-8 cm.; surface smooth, very 

 slightly sulcate, velvety, ferruginous, becoming homy and 

 glabrous and finally nearly black with age; margin subobtuse, 

 ferruginous, velvety; context woody, fulvous, 1-2 cm. thick; 

 tubes evenly stratified, 2-3 mm. long each season, fulvous, mouths 

 circular, 3 to a mm., edges obtuse, entire, ferruginous to fulvous; 

 spores globose, compressed on one side, hyaline, 5.5-6 x 4.5-5 m; 

 spines fulvous, 15-20 x 7-9 ai; hyphae 2.5 fi. 



On plum, birch and other trees. 



The decayed wood is red-brown and crumbles when crushed. 



F. fulvus oleae Lin. is injurious on olive in Italy. 



F. nigricans Fr."' ^ is very similar to F. igniarius from which it 

 differs chiefly in the black upper surface and the bluish or blackish 

 hymenial surface of the sporophores. Murrill'' regards it as a 

 variety of F. igniarius. 



As a wound parasite it causes a reddish-brown heart-rot of 

 deciduous trees, especially of willow, birch, poplar, beech. 



F. lucidus (Fr.) Bon. causes a cocoanut root-rot. 



F. fraxinophilus (Pk.) Sacc.«'' ^^ 



Pileus woody, subtriangular, compressed-ungulate, usually 

 deciurent, 5-10 x 6-12 x 2-4 cm.; surface white, pulverulent or 

 finely tomentose, concentrically sulcate, becoming gray or black 

 and rimose with age; margin tumid, white or yellowish, velvety to 

 the touch; context corky to woody, zonate, isabelline, 0.5-1 cm. 

 thick; tubes evenly but indistinctly stratified, 2-4 mm. long each 

 season, white when young, concolorous with the context in the 

 older layers, mouths white, subcircular, 2 to a mm., edges obtuse; 

 spores broadly ellipsoid, smooth, hyaline, thin-walled, 6-7 x 7-8 

 fi; hyphae light yellowish-brown, 10-12 /i; cystidia none. 



It causes a heart-rot of trunk and branches of species of ash. 



The starch in the host cells is lost early by diastatic action in 



