Longitudinal striation

These swellings and markings seem to be due either to the insertion of other cells adherent to the fibre or to mechanical manipulations to which the fibres themselves have been subjected. Slight longitudinal striations are also present in some cases, but these do not prevent observation of the more pronounced middle line marking the channel. On the whole the fibres appear smooth and semi-transparent. Their ends are pointed. 

Hemp. This is obtained from the bast fibres of Cannabis sativa. Under the microscope these fibres, which are usually joined in bundles, have a bruised cylindrical appearance and a diameter greater than that of flax fibres (Fig. 74, Plate VII). They are irregular as regards thickness and there are many longitudinal striations, which are sometimes so marked as to render difficult the observation of the internal channel, the latter being about one-third as wide as the fibres. Transverse striae are also observed often these do not traverse the whole width of the fibre and they arc not so regular in appearance as with flax. At the ends the fibres are usually rounded and sometimes slit down for a short distance. 

Angora wool. Cylindrical (with scales), longitudinal striation Absent Fine. 21-23 medium, 45... 

Camelidae (vicuna) wool Cylindrical, scales not very evident, longitudinal striations with fine granulations of pigment Thin, often interrupted 18-20... 

Rabbit s hair Cylindrical, scales not very evident, no longitudinal striation Full, interspersed with empty spaces, sometimes multiple 14-16... 

The most important sheeps wool is that of the Merino, remarkable for its thinness and for the great distinctness of the epidermal scales, which are cylindrical or semi-cylindrical. Since these scales have a very pronounced free edge, the fibre appears to have a toothed outline and the fibrous layer below is sometimes faintly apparent as a delicate longitudinal striation. The medulla is always lacking. 

Although apparently quite smooth and homogeneous, the fibres of ordinary silk show, when examined with a high magnification and with the aid of special disaggregating reagents, very fine longitudinal striation due to the fibrillary structure proper to all silks. This structure is especially apparent in wild silks even under a low microscopic power. 

Friedel (2) interpreted the transversal striations on oily streaks as small adjacent confocal domains that have a tendency to gather in lines. We already noted that such a situation exists in DADB (12) (but the lines are attached to the surface), and that c domains pin up on l lines moreover, oily streaks in cholesterics have clear confocal domains. However, the transversal striations on l or L lines are not compatible with c domains since we do not see there the typical Maltese cross on the contrary, the hyperbolic directions would be at a small angle to the sample plane if they exist. We do not reject FriedeFs explanation, but we must make it compatible with observations, particularly with the longitudinal striations. 

On the observe side of the breastplate are fiber shapes that are smooth and separate and exhibit some crimp (Figure 8). Some evidence of longitudinal striations on the formations is present inconsistency in size is found. They twist around each other while maintaining structural integrity. If the fiber shapes are bast, they have been subjected to some processing to separate them from their bundles. On the other hand, if the fibers occurred in the environment in somewhat the same structure as the pseudomorphs, that is, separate and individual, they would therefore be from a fiber class other than bast. 

Horn (cattle hom, etc.) Cream, browns to black in patches Almost opaque, except if in thin section, bleached or pressed Longitudinal striations Colours in fine stripes if bleached or very pale Slight fluorescence on pale areas... 

Rhino horn Mid-brown with fine stripes Only in thin sections, e.g. of fine carving Longitudinal striations Not possible Mosdy inert. Some fluorescence on outer surface... 

Flax fibres are multicellular, with each cell having tapering ends and a narrow lumen. The fibres show longitudinal striations and nodes (Fig. 1-13). The ultimate... 

Tussur is coarser than cultivated silk an outer sheath of gum is present, but this cannot be distinguished under the microscope. The brown discoloration, which seems to depend, to some extent, upon the source of food, is not confined to the gum but is distributed throughout the whole of the fibre. The cross-section is irregular, and longitudinal striations can be distinguished together with periodic constrictions. 

Viscose rayon spun by normal methods has a characteristic microscopic appearance (Fig. 6.16a). In the cross-section (Fig. 6.16b) it will be seen that the surface is deeply serrated, which gives rise to clearly-defined longitudinal striations. 

When examined under the microscope acetate fibres show no longitudinal striations. The cross-sections are irregular but more in the shape of lobes and the indentations are not so deep as in viscose (Fig. 6.19a and b). 

It is interesting to note that SEM observations revealed that the longitudinal striations present on the surface of the original cellulose remained on the surface of the carbon fiber, inspite of the variety of chemical transformations which had occurred. 

Care must be taken when analyzing by electron microscopy because the interferences are different from those in light microscopy and may structurally be very similar to asbestos. The classic interference is between anthophyllite and biopyribole or intermediate fiber. Use the same morphological clues for electron microscopy as are used for light microscopy, e.g. fibril splitting, internal longitudinal striation, fraying, curvature, etc. 

Fig. 4.12 Longitudinal sections of polyester fibers shown by TEM (A) do not have any interesting morphology, unstained, except for particles of 1102 (arrows). Impregnation with isoprene followed by OSO4 staiiung results in electron dense longitudinal striations and elongated voids (arrows) adjacent to the particles (B).

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