220 DISEASES OF TREES 



charcoal when dry, and may be rubbed down between the fingers 

 into an impalpable yellow powder. An important property which 

 it possesses is its great sponge-like power of absorbing water. 

 This is chiefly due to the fact that, owing to the cell-walls having 

 been perforated by the filamentous mycelia, the air is enabled to 

 escape in front of the water which enters by capillarity. Thus 

 it happens that when a house is attacked by M. lacrymans 

 the woodwork is able to absorb water with great ease, and to 

 transport it to considerable distances. Thus the capillarity of 

 the diseased wood makes it possible for liquid water to be 

 conveyed from the ground floor of a house to the upper stories, 

 which it may render damp by evaporation. So far wood that is 

 decomposed by M. lacrymans resembles that which is attacked 

 by what is popularly called dry-rot. 



M. lacrymans is, however, capable of growing out of the wood 

 in which it feeds, if only the surrounding air remains sufficiently 

 humid to prevent the advancing mycelial filaments drying 

 up. Where, therefore, the air is stagnant and humid, the 

 mycelium grows out of the wood, at first taking the form of a 

 snow-white loose woolly growth, which spreads over the wood 

 and covers its surface. These white fungus-growths also spread 

 on to other objects from which they can obtain no nutriment, 

 provided they are situated in the neighbourhood of the wood- 

 work. Thus they creep up the walls, and spread over the 

 damp ground, flag-stones, &c. Later on stouter branching 

 strands of the same colour occur amongst the masses of floccose 

 fungoid hyphae. These may attain to the thickness of the 

 finger, and are of immense importance in the life-history of 

 M. lacrymans. 



Before proceeding to describe these stout strands, I may 

 mention that the woolly mass of mycelia attains more consistency 

 as it gets older, and forms a lustrous silky ash-coloured sheet which 

 may be detached from the substratum. The ashy grey colour 

 of this mycelium enables us to distinguish it from that of 

 P. vaporarius, already described, which always remains white. 



The mycelial strands of M. lacrymans consist of (i) firm fibres, 

 which make them to a certain extent untearable, (2) filaments rich 

 in protoplasm, which in humid air may send out buds in all 

 directions, and (3) organs resembling vessels with large lumina, 



