204 BARKS. 



(100) Quillaia Bark. 



The secondary bast of Quillaja Saponaria, Molina (N.(X 

 Rosacese), to which portions of the dark-brown, outer bark are 

 sometimes attached. 



The bark presents the following structure : 



(1) Outer Bark, consisting of bands of cork cells alternating 

 with bands of brown parenchymatous tissue containing 

 numerous groups of bast fibres and large prismatic crystals 

 of calcium oxalate. 



(2) Bast Ring, completely traversed by medullary rays, usually 

 three or four cells wide, in which prismatic crystals of calcium 

 oxalate are occasionally to be seen. The bast rays -contain 

 numerous bast fibres, both isolated and grouped, together 

 with prismatic crystals of calcium oxalate, many of which 

 are of very large size (up to 1,000^, or even more in 

 length), and axially arranged. The groups of bast fibres 

 are very irregular in shape, and only occasionally stretch 

 from one medullary ray to the next. The individual fibres 

 vary very much in appearance, being often cut obliquely. 

 In transverse section they may be small (10-12^) or large 

 (40^) and rounded or angular, or they may be oval (60^) ; 

 the cavity may be a point or a slit. When isolated they 

 have a very characteristic irregular outline, exhibiting 

 remarkable enlargements ; they taper to a fine point and 

 near the apex are often forked ; with dilute mineral acid& 

 they assume a reddish colour. 



The sieve-tubes are comparatively wide, the sieve-plates large 

 and oblique. 



The diagnostic characters of powdered quillaia bark are : 



(a) The very large prismatic crystals of calcium oxalate. 



(b) The abundance of large bast-fibres of irregular shape, 

 c) The large sieve-tubes. 



