FUNGI IN GENERAL 99 



when the ground is not well clothed with snow, is succeeded 

 by an autumn in which the fleshy Fungi are considerably 

 reduced in numbers — that is to say, it is a bad Fungus 

 year. There may be other conditions — such as general low 

 temperature, absence of humidity, etc. — which seriously 

 affect the latent mycelium and, as in the years from 1890 

 to 1893, largely diminish the production of Agarics in the 

 autumn. 



The indurated tree Fungi, such as the Polyporei, are 

 also possessed in many cases of a copious mycelium which 

 penetrates and disintegrates the tissues of the wood. It may 

 be taken for granted that neither the arboreal Agarics nor the 

 Polyporei establish themselves, or can be developed from 

 healthy living tissue. The wood is at first dead at that 

 particular spot, and traversed by mycelium, before there is 

 any external appearance of the Fungus. There is no external 

 Fungus without an internal mycelium, but there may be a 

 very profuse mycelium and no external Fungus growth. In 

 this connection we may indicate that condition which is 

 popularly known as " touchwood," where the whole substance 

 is permeated by mycelium, and what at one time was hard 

 and firm oak or ash timber is rendered so friable that it 

 crumbles beneath the fingers. In tropical regions immense 

 masses of mycelium are produced from disintegrated timber, 

 long known under the name of Xylostrovia, extending for 

 many feet and of variable thickness, with a texture resembling 

 white leather. The conditions have all been favourable to the 

 vegetative system rather than the reproductive. As flowering 

 plants under exceptionally favourable conditions develop a 

 luxuriant growth without flowers or fruit, so the mycelium of 

 Fungi may also vegetate luxuriantly without producing organs 

 of fructification, until the vegetative growth is checked by 

 deficiency of humidity or some other cause. Another condi- 

 tion of mycelium was in past times regarded as autonomous, 

 under the generic name of Rhizomorpha. In this instance the 

 mycelium partakes of the character of long, branching or 

 anastomosing, rigid cords, with a dark or black exterior, often 

 growing between the bark and timber of dead trees, or 

 penetrating the timber in mines. It may extend for many 



