The Enemies of Trees 



are two abuses of the first magnitude. Beside these, man is 

 responsible for most forest fires. 



Cold is the barrier that sets a hmit to each species of trees 

 at a certain degree of latitude and at a certain altitude above the 

 sea. Few species are hardy enough to reach into British America, 

 or to climb high up on mountains. 



Frost damages forests by nipping the buds and tender shoots, 

 by actually causing tree trunks as well as branches to burst open 

 after the freezing of sap in spring, and by heaving the porous soil 

 so that saplings of all ages are uprooted. Frost often destroys 

 seeds before they are ripe, and while they are germinating. 



Snow and ice burden trees in winter time, doing great damage 

 to their tops — often maiming young trees for life. Broad- 

 leaved trees avoid much injury by their deciduous habit, but 

 evergreens suffer where snows are heavy and winters long. Ex- 

 treme toughness and flexibility of limb characterise trees that 

 successfully throw off their snow burdens spring after spring. 

 The Western mountain hemlock, crouching on the most exposed 

 ridges of the coast mountains, is a good example. 



Hail beats off the leaves and tender shoots of trees, especially 

 in the warmer states. It destroys flowers and unripe fruits, 

 and bruises young growth. 



Lightning shatters trees, and leaves them a prey to the 

 attacks of insects and fungi. The chief harm caused by it is the 

 starting of forest fires. Compared with this, the other damage it 

 does is slight. 



Winds lash the trees, breaking and maiming them. Hurri- 

 canes plough their paths through the woods. This exposes the 

 trees left on the border of the swath to a new danger. Their 

 support on the open side is gone; they fall by reason of the inade- 

 quacy of their roots to hold them securely in the ground. Roots 

 do not go deep unless they must. Winds fan small fires into 

 conflagrations. Beneficent carriers of pollen and distributors 

 of seed, they also carry infection from diseased trees to sound 

 ones, lodging spores in fresh wounds to eat down to the tree's 

 heart or to prey upon leaf or twig or bark. Each species finds 

 its habitat. 



Fungi are flowerless vegetable organisms that multiply by 

 spores. The mushrooms are the familiar fruiting organs of under- 

 ground species. Rust, mildew, blight and rot of fruit or of 



