84 ELEMENTS OF APPLIED MICROSCOPY. 
swollen that even the twists cannot easily be seen in a 
water-mount; they show more clearly, however, in air. 
3. Bast-fibres in General.— Most of the vegetable 
fibres in commercial use are derived from the bast-layer 
of the dicotyledonous flowering plants. 
The bast, or, as it is called by botanists, the phloem, is a 
fibrous layer lying just under the bark, and since it- is 
more or less developed in all the higher plants, it would 
be theoretically possible to obtain textile fibres from any 
one of them. In preparing the fibre from those herba- 
ceous plants actually in commercial use, the stems are 
first retted or allowed to ferment under water so that the 
gummy substances which hold the tissues together may 
be dissolved. Next they are scutched or exposed to the 
action of beaters which break up the outer and. inner 
friable tissues, leaving the elongated bast-cells adhering 
together in threads or bundles. The bast-fibre, as. we 
~ find it in commerce, is thus made up of a group of cells, 
not of a single cell like the cotton-fibre. 
When further broken up under the microscope, the 
bast-cell appears as a more or less elongated spindle 
with a central canal where the living protoplasm once 
lay, the cell wall of cellulose only being left. Both ends 
are symmetrically pointed. In size, proportions, cross- 
section, canal, and markings the bast-fibres of various 
plants may be distinguished. We shall consider briefly 
the six fibres which have most commercial importance— 
flax, hemp, Manila hemp, jute, ramie, and sisal. 
4. Flax.—Flax is obtained ‘from the stem of Linum 
usitatissimum, a tall lrerb widely cultivated in the central 
