26 GENERAL rnlNClPLES. 



dermis, gives to tlie young growth of trees its peculiar 

 color, by means of which the experienced cultivator is 

 enabled to distinguish varieties, even when not in leaf. 

 Within the corky layer is 



3. The Green Lnyer [E), which gives to the young 

 shoots their green color. Tliis, as the wood ripens, is 

 soon covered by the corky layer. 



The Inner Barh, or Liber {F). — This is the interior 

 portion of the bark, in immediate contact with the wood. 

 It is composed of perpendicular layi-rs of soft, flexible 

 but very tough fibres. It is this part of the bark of the 

 Basswood that is used lor tying hi budding, etc., the tissue 

 being separated by mnceiatioii. 



Tiie bark remains with these distinct layers, only for a 

 few years. It scales off, and falls away in forms var} ing 

 with the kind of tree, but in all cases a poition of the in- 

 ner bark is left attached to the tree. In the grape-vine, 

 the inner bark, or liber, is renewed each year, and that 

 formed the year before is thrown oft' in long shreds. 



Within the bark we have the wood, and in the center 

 the pith. The wood is divided into 



1. The Sap-ioood (included in the dotted line B). — This 

 is the youngest, or last formed, layer of wood, immediate- 

 ly helow the hnier bark. It is distinguished in all trees 

 by being softer and lighter colored than the older parts. 



2. The Heart, or Perfect wood. — This is the central, 

 or interior portion of the stem, or branch, grown firm and 

 mature by age. It is generally a sliade darker in color 

 than the newly formed part, or sap-wood. As the en- 

 graving, fig. 2, shows a stem only one year old, this is 

 not represented. 



8. The Pith (6^).— This is the soft, sp-ngy substance 

 in the center of the stem and branches. In soft-wooded 

 species, like the grape-vine, it is large ; in hard-wooded 

 species, as the a|)i)le, pear, quince, etc., it is small. In young 

 siioots it is soft, green, and succulent, and fills an impor- 



