1). We know
it is a tube, because on taking a thin, narrow slice across a fibre and
examining the slice under the microscope, we can see the hole or
perforation up the centre, forming the axis of the tube (see Fig. 2).
Mr. H. de Mosenthal, in an extremely interesting and valuable paper (see
_J.S.C.I._,[1] 1904, vol. xxiii. p. 292), has recently shown that the
cuticle of the cotton fibre is extremely porous, having, in addition to
pores, what appear to be minute stomata, the latter being frequently
arranged in oblique rows, as if they led into oblique lateral channels.
A cotton fibre varies from 2.5 to 6 centimetres in length, and in
breadth from 0.017 to 0.05 millimetre. The characteristics mentioned
make it very easy to distinguish cotton from other vegetable or animal
fibres. For example, another vegetable fibre is flax, or linen, and this
has a very different appearance under the microscope (_see_ Fig. 3). It
has a bamboo-like, or jointed appearance; its tubes are not flattened,
nor are they twisted. Flax belongs to a class called the bast fibres, a
name given to certain fibres obtained from the inner bark of different
plants.
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