LECTURE III. 



HOW TREES GROW. 



The technical part of the art of forestry is called silviculture the art 

 that produces the wood-crop for the management of the forester. For an 

 understanding of the treatment of trees en masse, the forester needs a 

 knowledge of dendrology, the knowledge of trees in all details, and espec- 

 ially their life history, individual and in association. Often wrongly de- 

 fined in terms of size, the tree is potentially existing already in seed and 

 seedling it is a woody plant, the seed of which is capable of producing a 

 single stem from the ground with a definite crown. 



Trees, growing from seed, are built up from cell growth, division and 

 multiplication like other living organisms, and they have similar require- 

 ments. Unlike other plants, they have longer life and attain greater 

 height, to lift their foliage to the light. Their remarkable height is built 

 up, storey by storey, by shoots, wh ich push out from buds and elongate 

 from the tips of stem and branch. The age of the tree may thus be told, at 

 least in young specimens, by counting the annual shoots, which are marked 

 off from each other by a swelling of the stem. 



Buds are developed at the end of the year's growth, the terminal bud 

 or one near the end of the shoot annually continuing the height growth. 

 Each class of tree has a different habit of bud development, and trees can 

 be identified by their buds alone. The Conifers, with fewer lateral buds, 

 than the deciduous trees, persistently develop the main stem at the expense 

 of the branches, the shoot from the single terminal bud making rapid 

 height growth. If the terminal bud of a pine be destroyed, the side buds 

 usually carry on the growth and cause forking of the stem. Among hard 

 woods the majority of the buds do not develop, but are either lost or 

 remain dormant, the shape of the tree being dependent upon this bud 

 development, so that the dense crown of the Beech from the development 

 of many buds has a different appearance from the open crown of an Oak. 

 The dormant buds remain undeveloped, continually pushed out beyond the 

 wood of the surface each year, ready in case of necessity or accident finally 

 to develop into shoots. 



As the new buds are formed at the ends of the shoots each year, the 

 tree might grow on forever, if each species did not grow within certain 

 definite height limits, which depend on conditions of soil, climate and spe- 

 cies. The moisture from the soil, the tree must raise to its foliage against 

 gravity, and the height to which the water can be lifted is limited ; some 

 species offering more friction to the water current, cannot grow as high as 

 others. 



