Handbook of Nature Study Notes 5 - on Trees

    I've decided our focus this term will be Trees. Here are a few of the things I've learned by reading the introductory section in the Handbook of Nature Study:

• Parts of the tree:
• The head, or crown, is composed of the branches as a whole, which in turn are composed of the larger and smaller branches and twigs.
• The spray is the term given to the outer twigs, ..which bear the leaves and fruit.
• The branches are divisions of the bole or trunk, which is the body or stem of the tree.
• The bole at the base divides into roots, and the roots into rootlets, which are covered with root hairs.
• The roots:
• First, they absorb the water and minerals from the soil (through the root hairs)
• Second, they hold the tree in place against the onslaught of the winds.
• There is as much of the tree hidden below ground as there is in sight above ground. 
• The trunk, or bole:
• First, it holds the branches aloft...to expose the leaves to the sunlight.
• Second, it's a channel by which the sap surges from root to leaf and back again.
• The branches are divisions of the trunk and have the same work to do.
• A trunk cross-section:
• First, there is the outside layer of protective bark.
• Next comes the cambium layer. It builds on its outside a layer of bark and on its inside a layer of wood around the trunk.
• Then there is a lighter coloured portion of the trunk called the sapwood, because it's filled with sap, which moves up and down its cells in a mysterious manner. The sapwood consists of the more recent rings of annual growth.
• Within the sapwood are concentric rings to the very centre or pith; this portion is usually darker in colour and is called the heartwood; it no longer has anything to do with the life of the tree, but simply gives to it strength and staunchness.
• Leaves:
• A leaf would be of little use unless it could be reached by the sunlight.
• It's made up of the petiole and the blade, or widened portion of the leaf, which is sustained usually with a framework of many ribs or veins. 
• The petioles and the veins are sap channels like the branches and twigs.
• The leaf is a factory; the raw materials are taken from the air and from the sap containing minerals from the soil; the finished product is largely starch, which is plant food. The starch is then stored in sapwood to be used for the growth of the next year's leaves. 
• By midsummer most of the tree's work is done. The chlorophyl in the leaf cells has been safely withdrawn and secluded in the woody part of the tree. The autumn leaf which glows gold or red has in it only the material which the tree can no longer use.
• A thin, corky layer develops between the petiole and the twig, and when this is perfected the leaf drops from its own weight at the touch of a slight breeze. 
• Growth:
• Each year the tree pushes higher, deeper and wider through the tips of the twigs and rootlets.
• There is also a layer of growth over the entire tree - roots, trunk, branches and twigs - each year, as if a thick coat of paint has been put over the whole tree. 
• Prevailing winds cause the tree to grow more luxuriantly on the leeward side.