Children's Department 



Devoted to imparting information about trees, woods and forests to boys and girls so that they may grow to know 

 how necessary trees are to the health, wealth and future of their country. 



By Bristow Adams 



HOW A TREE GROWS 



THROUGHOUT its life a tree grows only at the 

 tips of the twigs and at the tips of the rootlets. 

 When any part except the very end of stem, or 

 branch, or root is once formed, it keeps its same place 

 and grows neither up nor down. Thus a nail driven into 

 a tree trunk will always be the same height from the 

 ground, no matter how old the tree may become. While 

 the tree may push up higher or down deeper, its branches 

 cnce formed remain in exactly the same position which 

 they had when they first sprouted. Many persons suppose 

 that the whole tree pushes up in height. Not many years 

 ago there was a story current that a man had set his 

 barn upon willow posts, and that the posts grew up in 

 the air so that at the end of a few years he boarded in 

 the lower part of the barn and had another story. This 

 process continued indefinitely until he had a regular sky- 

 scraper, and then converted it into a silo. While this 

 story may have started as a joke, it was repeated in many 

 newspapers and periodicals as an interesting fact. That 

 it is not true is proved by the fact that "blazes" or axe- 

 marks cut in the bark of trees by our earlier surveyors 

 have remained in exactly the same position for hundreds 

 of years, perhaps being grown over by the bark as the 

 tree increased in girth. 



THE PARTS OF A TREE 



A tree is composed of three parts, the head or the 

 crown, the trunk or bole, and the roots. Each one of 

 these three parts is further divided into other parts; in 

 the crown are branches which in turn form into branch- 

 lets, and these into finer sprays or twigs which bear the 

 leaves and fruit. Just as the branches are divisions of 

 the bole or trunk, so the roots are divided into rootlets 

 which are covered with root hairs. 



Each of these parts is necessary and helps to carry on 

 the tree's life. The roots have two purposes: First, they 

 absorb the water which contains the tree food that comes 

 out of the soil ; and, second, they hold the tree in place 

 by anchoring it firmly to the ground. Some trees, such 

 as the maple, have wide-spreading roots that keep near 

 the surface; others like the hickory develop a deep tap- 

 root which goes almost straight down. 



THE trunk or stem also has two duties to per- 

 form. It holds the branches up, and rises to a 

 sufficient height so that it can bear these branches 

 and leaves where they can get the sunlight. In the for- 



ests, the topmost branches of the tree extend farthest, 

 reaching up and up to the sunlight. For this reason, the 

 trees which grow in dense woods, closely surrounded by 

 their neighbors, are usually straight, and tall, and free 

 from side branches. The forest-grown tree is the one 

 that is most useful to the lumberman because from it 

 he can get long, straight boards and poles, without knots 

 and cross grains, which are made by branches that grow 

 out from the stem. 



A tree which grows in the open can find its light on all 

 sides, and it thus reaches out with limbs that extend 

 along the trunk from the ground to the very top, getting 

 the greatest amount of sunlight from all sides as well as 

 from the top. These round, short, low-headed trees are 

 of the kind which grow in open meadows ; under them 

 the cattle find grateful shade in summer. 



The second duty of the trunk is to form, with the 

 branches, the channels through which the food material? 

 go from roots to leaves, and back again, through each 

 growing part. In cross section, the trees shows on the 

 outside a layer of bark which protects it from injuries. 

 The bark is not alive and cannot stretch with the growth 

 of the tree, so that it gradually cracks and breaks up into 

 plates or ridges, but it is being constantly built up by 

 new layers from the inside. The very thin layer next to 

 the bark, known as the cambium, is the living, vital part 

 of the trunk. It builds on its outside this layer of bark 

 and, on its inside, a layer of wood around the trunk. 

 Just inside this cambium layer is what is known as the 

 sapwood, which is generally lighter in color than the 

 middle part of the tree, or heartwood, and is made up of 

 a number of rings of growth, one of which the tree puts 

 on every year. Within this sapwood the sap moves up 

 and down and this part of the tree is, like the cambium, 

 a living portion of the growth. Inside the circle of the 

 sapwood are other rings of heartwood to the very center. 

 This heartwood portion no longer has life, but serves its 

 purpose as a column of strength and support. 



The leaves grow on the outermost portions of the tree, 

 since they must be where they can receive the sunlight. 

 It is for this reason that the trunk lifts the branches on 

 high, and the branches hold the twigs far out, and the 

 twigs divide into the finer sprays so as to spread the 

 leaves and hold them well into the sunlight. 



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