INFLUENCES AND EFFECTS. 223 
their appearance in species almost innumerable, sending their 
subtle threads of mycelium deep into the tissues of the woody 
substance, and the whole mass teems with new life. In this 
metamorphosis as the fungi flourish so the twigs decay, for the 
new life is supported at the expense of the old, and together 
the destroyers and their victims return as useful constituents to 
the soil from whence they were derived, and form fresh pabulum 
for a succeeding season of green leaves and sweet flowers. In 
woods and forests we can even more readily appreciate the good 
offices of fungi in accelerating the decay of fallen leaves and 
twigs which surround the base of the parent trees. In such 
places Nature is left absolutely to her own resources, and what 
man would accomplish in his carefully attended gardens and 
shrubberies must here be done without his aid. What we call 
decay is merely change; change of form, change of relationship, 
change of composition; and all these changes are effected by 
various combined agencies—water, air, light, heat, these furnish- 
ing new and suitable conditions for the development of a new 
race of vegetables. These, by their vigorous growth, continue 
what water and oxygen, stimulated by light and heat, had 
begun, and as they flourish for a brief season on the fallen 
glories of the past summer, make preparation for the coming 
spring. 
Unfortunately this destructive power of fungi over vegetable 
tissues is too often exemplified in a manner which man does not 
approve. The dry rot isa name which has been given to the 
ravages of more than one species of fungus which flourishes at 
the expense of the timber it destroys. One of these forms of 
dry rot fungus is fe) ulius lacrymans, which is sometimes spoken 
of as if it were the only one, though perhaps the most destruc- 
tive in houses. Another is Polyporus hybridus, which attacks 
oak-built vessels ;* and these are not the only ones which are 
capable of mischief. It appears that the dry rot fungus acts 
indirectly on the wood, whose cells are saturated with its juice, 
aud in consequence lose their hgnine and cellulose, though their 
walls suffer no corrosion. The different forms of decay in wood 
* Sowerby’s ‘* Fungi,” plates 289 and 287, fig. 6. 
