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 
ornon-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 are 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 (1) 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 different plants vary 
considerably in size and form. As a rule, the fibres when sepa- 
rated are free of crystal cells and crystals. This 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. 
