90 HISTOLOGY OF MEDICINAL PLANTS 



structure. Such a classification is logical and accurate, because 

 it is based upon permanent characters. Another character used 

 in classifying bast fibres is the nature of the cell, whether branched 

 or non-branched. In fact, this latter character is used to separate 

 all bast fibres into two fundamental groups — namely, branched 

 bast fibres and non-branched bast fibres. The third important 

 character utilized in classifying fibres is the presence or absence 

 of crystals. 



Bast fibres are classified as follows: 



1. Crystal bearing. 



2. Non-crystal bearing. 



The crystal-bearing fibres are divided into two classes: 



1. Of leaves. 



2. Of barks. 



The non-crystal bearing are divided into: 



1. Branched. 



2. Non-branched. 



The branched and non-branched arc divided into four classes: 



1. Non-porous and non-striated. 



2. Porous and non-striated. 



3. Striated and non-porous. 



4. Porous and striated. 



CRYSTAL-BEARING BAST FIBRES 



The crystal-bearing fibres are composed (i) of groups of 

 fibres, (2) of crystal cells, and (3) of crystals. In these cases 

 the groups of fibres are large, and they are frequently completely 

 covered by crystal cells, which may or may not contain a crystal. 

 The crystals found on the fibres from the difterent plants vary 

 considerably in size and form. As a rule, the fibres when sepa- 

 rated are free of crystal cells and crystals. Tliis is so because 

 the crystal cells are exterior to the fibres, and in separating the 

 fibres during the milling process the crystal cells are broken down 

 and removed from the fibres. It is common, therefore, to find 

 isolated fibres and crystals associated with the crystal-bearing 

 fibres. The fibres which are crystal-bearing may be striated 

 or porous, etc.; but owing to the fact that the grouping of the 

 fibres and crystals is so characteristic, little or no attention is 

 paid to the structure of the individual fibres. 



