THE STEM. 5 



paper, and is easily separated from the parts beneath it. 



In some species, as the 

 grape vine, for example, 

 this rind is shed and re- 

 newed annually, whilst 

 in others, as the apple, 

 pear, tfec., it unites with 

 the layer of tissue b- 

 . 2, hair of the hori- ^^<^ffl neath it, and forms a 



if rind. B. inner bark or Substance, USUallv Call- 



Ijbor. C. sap-wood or last j ,-77 1 l 



formed layer. D, perfect wood. E, pith. F, ^COHlCal layers, which 



vertical section of a five year old stem, showing Separate from the tree 



Delayers of perpendicular woody tubes or at diff erent periods, aC- 



cording to the age of the 

 subject and other circumstances. 



It is these cortical layers that give rise to the expres- 

 sions smooth and rough back. 



2. The Inner BarTt, or Liber (B} This is the interior 

 portion of the bark in immediate contact with the wood. 

 It is composed of perpendicular layers of soft, flexible 

 fibres, filled up with tissue. It is this part of the bark of 

 the Basswood that is used for budding ties, &c., the tissue 

 being separated from the woody fibre by maceration. 



3. The Sap-wood (C.} This is the youngest or last- 

 formed layer of wood, immediately below the inner bark. 

 It is distinguished in all trees by being softer and lighter 

 colored than the older parts. 



4. The Heart or Perfect-wood (D.} This is the central 

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

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

 than the newly-formed part or sap-wood. 



5. The Pith (E.) This is the soft, spongy substance 

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

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



