48 DISEASES OF DECIDUOUS FOREST TREES. 



spreads outward. The discolored areas gradually disintegrate until 

 the wood becomes straw-yellow. In the final stages of the disease the 

 entire heartwood becomes converted into a soft rotted mass which 

 resembles pith in its consistency. 



The catalpa disease is caused by Polystictus versicolor Fr. The 

 spores of this fungus germinate in some wound, or generally at a 

 branch stub. The fungus grows through the stub and spreads up 

 and down in the trunk. After a time fruiting bodies form on the 

 outside of the trunk, generally near a branch wound. The sporo- 

 phores are sessile and a great many of them grow together, one above 

 the other. They are readily recognized by the soft, hairy upper 

 surface, with alternate bands of light and dark color. The margin 

 of the sporophore is irregularly wavy when dry. Fresh sporophores 

 are fleshy, but as they grow older they become tough and somewhat 

 brittle, and the front edge curls in. 



Hardy catalpa trees are affected early in life. In the instances 

 described the trees were about 18 years old. In order to prevent 

 the spread of the disease most attention should be paid to the careful 

 coating of all wounds made in pruning or in cutting off root suckers. 



HEART-ROT OF OAKS CAUSED BY FOMES EVERHARTII. 



Fomes everhartii Ellis & Galloway (16) has been found repeatedly 

 growing on blackjack oak (Quercus marilandica Muench.), causing a 

 disease almost indistinguishable from that described for the false- 

 tinder fungus (Fomes igniarius). Affected trees frequently show in a 

 very striking manner that the mycelium of this fungus is capable of 

 growing into the sapwood of the living tree (PI. Ill, fig. 2). In the 

 upper part of the figure it will be noted that the fungus has destroyed 

 not only the heartwood but has extended through the sapwood, 

 where it has evidently been growing for about three years, as indi- 

 cated by the callous formation on the edges of the diseased part. 



The sporophores of Fomes everhartii are large, conspicuous woody 

 bodies which grow out from wounds. They are generally broad, of 

 a dark rusty brown color, with a deeply cracked and fissured upper 

 surface. The lower surface is red-brown in color, with extremely 

 minute round pores. 



WHITE-ROT CAUSED BY POLYPORUS SQUAMOSUS. 



Buller (9) has recently described a white-rot of deciduous trees 

 caused by Polyporus squamosus Huds., which occurs upon the maple 

 (Acer pseudoplatanus L., A. platanoides L., A. saccharinum L., A. 

 negundo L.), pear (Pyrus communis L.), oak (Quercus sp.), elm ( Ulmus 

 montana With.) , walnut (Juglansregiah.), linden ( Tilia europaea Jj.), 



149 



