THE- STEM. 



5 



,i,iiii,.:jiii,i,liliJiiiatyi 



Fig. 2 F. 



Fig. 2, half of the hori- 

 ■,*ntal section of a five year 

 vM stem. outer bark 

 tiT rind. B, inner bark or 

 libor. C. sap-wood or last 

 formed layer. D, perfect wood. £, pith. F, 

 vertical section of a five year old stem, showing 

 the 6.tt) layers of perpendicular woody tubes or 

 fibres. 



Fig. 2. 



paper, and is easily separated frora tiie 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, 

 pear, &c., it unites with 

 the layer of tissne be- 

 neath it, and forms a 

 hard, scaly, or corky 

 snbstance, nsnally call- 

 ed cai'tical layers^ which 

 separate from the tree 

 at different periods, ac- 

 cording to the age of the 



subject and other circmnstances. 



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

 sions smooth and rougJi back. 



2. TTie Inner Bark 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 np \rith tissne. 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 Sajp-^oood {C) — This is the youngest or last- 

 fonned 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-ivood {Z>.) — This is the centi-al 

 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-fM'med ^lart or sap-wood. 



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

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

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



