28 



PHARMACEUTICAL BOTANY 



Fig. 22. — Part of a cross-section through 

 branch of Cytisus loburnum. (The branch was 

 cut from the tree at the end of October.) From 

 A to E the last annual ring of wood; from A to 

 B the spring growth with large tracheal tubes 

 (r, T, T); between B and C and D and D are 

 wood-fibers; between C and D and D and E, 

 wood parenchyma; from E to F, canbium; F to 

 G, phloem portion; G to H, cortical parenchyma; 

 M medullary ray. Below A the last wood- 

 fibers and wood parenyma formed the previous 

 year. {From Sayre after Haherlandt.) 



lessened and small ducts and 

 much mechanical woody 

 fibre are formed. Thus the 

 open, loosely arranged prod- 

 uct of the spring growth 

 abuts on the densely ar- 

 ranged product of the last 

 summer and autumn growth 

 and the sharp contrast 

 marks the periods of growth. 

 To the two different regions 

 of growth is given the 

 term of "annual ring." By 

 counting the number of 

 these rings it is possible to 

 estimate the age of the tree 

 or branch. 



Bark. — Bark or bork is a 

 term applied to all that por- 

 tion of a woody exogenous 

 plant axis outside of the 

 cambium line. 



In pharmacognic work, 

 bark is divided into three 

 zones, these from without 

 inward being: 



1. Outer Bask or Cork. 



2. Middle Bark or Cor- 

 tical Parenchyme. 



3. Inner Bark or 

 Phloem. 



Commercially, bark is 

 divided into two zones, 

 which are, passing from with- 

 out inward: 



I Outer Bark (Cork). 



2. Inner Bark (Cortical 

 Parenchyme and Phloem). 



