FIRST LESSONS IN FRUIT GROWING. 



>7 



Fig. 2213 (from Primer of Forestry, by Pinehot.) 

 Cross-section of Black Oak. The silver grain, 

 the rings of annual growth, and the' dark heart 

 wood and lighter sapwood are visible, and the 

 line between the rough, corky outer bark and the 

 thinner and lighter colored inner bark may be seen. 



The heart wood is not essential to the 

 growth of the tree, except to give it stiffen- 

 ing and strength. Old trees may often be 

 found making good annual growth when 

 the heart wood is rotted away, leaving the 

 trunk quite hollow. 



Tne Sapwood, so called because it con- 

 tains the moving sap of the tree, is the 

 outer or new wood next to the bark. It is 

 softer and more sappy than the heart wood, 

 and is usually easily distinguished from it 

 by its lighter color. 



The Fiber or Inner Bark, is a thin layer 

 of bark next to the sapwood. It is com- 

 posed of a number of layers of soft, flexible, 

 but very tough fibers. In some kinds of 

 trees it is much more prominent than in 

 others. In the basswood it is quite plen- 

 tiful, and at one time was used largely for 

 strings in greenhouse and nursery practice, 

 but the fibre of the Raffia palm is now used 

 in place of it. 



The Rind or Outer Bark, as it 

 appears upon a young stem or branch 

 is made up of three thin layers. On 

 the outside is a soft green layer, which 

 gives the green color to fresh grow- 

 ing shoots. On the outside is the 

 epidermis, or cuticle, a thin, smooth, 

 transparent covering like tissue paper. 

 Between these is the corky layer, 

 which does not show at first, but 

 gradually develops as the wood ripens, 

 and hides the green layer beneath it. 

 This corky layer is at first usually of 

 some shade of brown, and gives to 

 the young wood its peculiar color, by 

 which an experienced grower may 

 readily distinguish varieties by the 

 bark alone. The bark of the North- 

 ern Spy apple tree, for example, is 

 a dark, reddish brown, while that 

 of the Yellow Transparent is of a brown- 

 ish yellow. 



On the surface of the bark of young stems 

 may often be noticed small oval spots or 

 patches, usually of a diff'erent color from 

 the epidermis. These are the lenticles, 

 formed by a group of corky cells. In the 

 cherry they are very large and prominent, 

 forming horizontally on the trunk ; on the 

 apple they are smal- 

 ler and more num- 

 erous and form per- 

 pendicularly. 

 the shedding of 



THE bark. 



The bark retains 

 these three distinct 

 layers only for a 

 short time. As the 

 tree or branch be- 

 comes older, the 

 corky layer gradu- 

 ally increases in 

 thickness, and after 

 a time bursts the 

 epidermis, and be- 



Fig. 2214. 



The deeply ridged bark of 



the locust (after Craig). 



