368 NATURE-STUDY 



toadstools, fungous incrustations, and lichens growing upoa 

 the dead logs and stumps, and even on the sick, yet hving, 

 trees. The noticeable fungous growth which we see on the 

 outside is merely the fruiting portion, which is a part of 

 a larger mass of fungous fibres and filaments that spread 

 under the bark and within the wood of the tree. This 

 invisible part of the fungus is what does the chief work of 

 decay. Sometimes by removing the loose bark of a decay- 

 ing log the white vegetative part of the fungus may be seen. 

 Fungi perform a useful work in removing the dead timber 

 that otherwise would so litter the ground that no more growth 

 could come up. Besides the fungous decay there is also 

 chemical oxidation of the wood which hastens the disin- 

 tegration. 



The ground beneath the trees is covered with a thick 

 deposit of matted and felted leaves. Dig up this leaf mass. 

 Notice on the surface the recently fallen leaves, then, below, 

 the leaves of former years more aged and decaying. Still 

 farther down the leaves are crumbling, and soon the leaf 

 form can no more be made out. The lowest part is com- 

 posed of a Ught porous mass of black material, which is the 

 result of the decay of the leaves. This black substance is 

 called leaf mould, and consists largely of carbon, which 

 gives it its black color. This mould is very fertile, and is 

 used by gardeners for potting and bedding plants. A forest 

 thus fertihzes itself by the fall and decay of its leaves. 



The trees in a forest influence each other's growth. A 

 tree grown in the open, with plenty of light from all sides 

 and elbow room, is not as tall and slender as it would have 

 been had it grown among other trees. In the forest the 

 trees contend with each other for the light, and try to over- 



