THE STEM. 



ii!i{|.ii;iiii 



ttiJJiiililliiiilljii^ilHiliiiiiiJiiliS 



Fia. 2 F. 



F!g. 2, half of the hori- 

 zontal section of a five year 

 old stem. ^5, outer bark 

 or rind. B, inner bark or 

 liber. C. sap-wood or last 

 formed layer. D, perfect wood 



Fig. 2. 



E, pith. F, 



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



In some species, as the 

 grape vine, for example, 

 this rind is shed and re- 

 newed annnally, whilst 

 in others, as the apple, 

 l^ear, &c., it nnites with 

 the layer of tissne be- 

 neath it, and forms a 

 hard, scaly, or corky 

 substance, usually call- 

 ed cortical layers^ which 



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

 ^hejve layers of perpendicular woody tubes or ^^ different pCriods, 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 Baric 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. T7ie 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 Pitli {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 



