COMMON AGARIC. 



251 



Fig. 69. 



sometimes over 3 ft. long, with a hard upper crust and soft spongy inner 

 tissue. Many other species attack broad-leaved trees. 



Polyporus sulphureus is a " red-rot" wound-parasite on Oak, Willows, 

 Poplar, and Birch chiefly, also other broad -leaved trees, and Conifers. The 

 large, fleshy or cheese-like, bright sulphur-yellow or reddish-yellow sporo- 

 phores appear annually at old branch-holes or on the stem, assuming 

 different forms, and varying up to 2 ft. long. Polyporus vaporarius is 

 another "red-rot" wound -parasite chiefly in Conifers, and also destructive 

 as a saprophyte in timber 

 lying in the woods (like 

 Merulius lacrymans, which 

 is seldom parasitic ; but the 

 mycelium of the latter soon 

 changes from white to grey, 

 while that of P. vaporarius 

 always keeps white). Its 

 sporophores form flat, thin, 

 white incrustations on the 

 bark of the trees infected. 



* The Beech Stump-tuft 

 or common Agaric, Agaricus 

 mdleus (Figs. 68, 69), an 

 edible mushroom growing 

 saprophytically on dead 

 stools and roots of old trees 

 (especially Beech), is a 

 common and often very 

 destructive parasite in young 

 Conifer crops, especially 

 Scots Pine, and mostly 

 attacks plantations of 4 to 

 15 years old. As first signs 

 the leaves of the infected 



plant, pole, or tree turn yellow, wither, and fall ; then the shoots wither 

 and the butt of the stem swells, the bark fissures, resin exudes and flows 

 to the ground, the cambium is killed, and finally the infected poles or 

 trees usually die either in spring or in autumn, while rhizomorphs pervade 

 the rotting wood and the soil round about, even when no tawny yellow 

 mushrooms appear. 



This disease breaks out in patches and rapidly kills young plants in full 

 vigour. The honey - yellow or dirty yellow -brown mushrooms (pilei} 

 with dark-brown hairy scales and yellowish-white lamellae, which turn 

 flesh-coloured, or on which reddish-brown spots form later, appear in 



Natural 



a. Part of a Scots Pine root killed by Agaricus 



melleus, and showing an external rhizo- 

 morph penetrating the root at a. 



b. Flattened internal rhizomorphfrom between 



bark and dead "wood. 



