2 26 PLANT LIFE. 



flat fructification (not mushroom-like), originally broke 

 up dead logs in forests ; but it is generally found in 

 houses, where it is much dreaded, as it often destroys 

 the whole of the woodwork. In many cases the wood 

 attacked by this fungus breaks into lines crossing at 

 right angles. This is a useful sign of the existence of 

 dry rot. A plentiful supply of air generally prevents 

 its development, but, once in the woodwork, it can 

 scarcely be exterminated. 



Several of the ordinary mushroom-like fungi destroy 

 living trees. They generally work in the same sort of 

 manner ; and, having once obtained an entrance through 

 the cork sheath, they grow everywhere up and down 

 amongst the soft tissues, so that the tree eventually 

 decays and dies. They spread from one tree to 

 another, either by the spores, which are carried by 

 wind or insects to some wound on the bark of a tree, 

 or else by growing through the soil and attacking the 

 roots. Agaricus inelleus, for instance, often attacks trees 

 in this manner. If the bark of a tree attacked by 

 it is torn off, peculiar blackish-brown flattened fibres 

 from tV to \ of an inch in diameter are usually found. 

 These, rhizomorphs, are composed of mycelium 

 threads agglutinated together. They grow out of the 

 root of an infected plant into the soil ; and then 

 through the soil to the nearest roots, which they 

 penetrate ; and so they infect fresh and quite un- 

 injured trees. Hence the importance of recognising 

 and destroying these parasitic fungi is very great. It 

 is also advisable not to plant woods of only one species 

 of tree, as these fungi are often confined to one kind 

 of tree, and in a mixed wood they are not so likely to 

 be able to pass easily from tree to tree. 



Others of these fungi are practically servants of the 



