300 Studies in Forestry [CHAP. xm. 



III. FUNGOID DISEASES OF THE ROOTS AND THE BASE 



OF THE TRUNK. 

 A. On Conifers: 



i. Agaricus melleus, L., the Honey Fungus, one of the 

 edible Mushrooms. This is a very common and, in many 

 localities, a very dangerous parasite in young coniferous crops, 

 especially on Spruce, Scots and Weymouth Pines, and Larch, 

 though seldom to be found on Black Pines. It also occurs 

 extensively as a saprophyte on dead stools and roots of old 

 trees, particularly on Beeches. It appears mostly in young 

 crops of from four to fifteen years of age, but may also be 

 found in mature stems of 100 years old. Close sowings and 

 plantations formed with wisps of seedling Spruce suffer most 

 from the disease. It is apt to be frequent in localities where, 

 owing to deterioration of the soil, a coniferous crop is formed 

 after a fall of broad-leaved timber, on the roots and stools 

 of which the mushrooms or 'toad-stools' have developed 

 saprophytically. 



The first symptoms of the disease consist in the gradual 

 yellowing, withering, and shedding of the needles. This is 

 followed by withering of the shoots, swelling of the root-stool, 

 fissuring of the bark, resinous outflow on the ground, rotting 

 of the cambium, and finally the death of the plant, which 

 usually occurs either between the middle of April and the 

 middle of June, or else between the middle of October and 

 the middle of November. 



The blackish-brown mycelial filaments of this partly sapro- 

 phytic fungus, by extending themselves under the bark of the 

 stool and roots, and throughout the soil, manage to effect 

 a foothold on the roots with which they may come in contact ; 

 and then, boring their way through the bark, they commence 

 their attacks as a parasitic fungus by forming long, white, flat 

 rhizomorphous mycelial filaments developing between the 

 sapwood and the cambium. Such rhizomorphous develop- 



