20 



PKACTICAL FORESTRY. 



trees, their stems and branches increase in diameter by 

 the annual formation of a new layer or ring of wood, de- 

 posited on the outside of that of the preceding year — 

 hence the name of the outside growers. 



The root at first is but a single descending axis, grow- 

 ing downward and absorbing nourishment from the sur- 

 rounding soil, for the support of the ascending axis or 

 stem. This condition or form of root exists for only a 

 .period, varying from a few hours to a few days; for, 

 from this central root or radicle of seedlings, side or 

 lateral roots are emitted, not only as it would appear in 

 search of nutriment, but to more firmly fix the plant in 

 the soil. This central, or as it is more commonly termed 

 among nurserymen and arboriculturists, tap-root, may 

 continue to elongate for years, and penetrate the earth 

 to the depth of several feet, or it may cease to grow 

 when the plant is only a few weeks or months old, all 

 depending upon the character of the soil, or the habit of 

 the tree under cultivation. 



The side or lateral roots, however, continue to elongate 

 as long as the tree lives, for it is the newer or younger 

 roots that are always the most active in absorbing nutri- 

 ment, the more rapid their development and multiplica- 

 tion, the more rapid is the growth of the whole tree. 



That portion above ground is at first but a simple 

 stem bearing only leaves, but as it increases in hight and 

 age, buds are formed on the central axis and from these 

 springs branches, and this multiplication of branches and 

 buds continues throughout the entire life of the tree. The 

 first buds formed on the stem may or may not produce 

 branches, depending on circumstances, but as a rule only 

 a few of the uppermost do so, and the others are over- 

 grown and smothered. 



As a whole, a tree may be said to consist of roots, 

 stem, branches, buds, leaves, flowers, and fruit, with 

 bark surrounding all the ligneous parts. This bark is at 



