Comparative anatomy of the barks of the salicaceae. Pt. 1 / by Pierre Élie Félix Perrédès.

  • Perrédès, Pierre Élie Félix.
Date:
[1903.]
Catalogue details

Licence: In copyright

Credit: Comparative anatomy of the barks of the salicaceae. Pt. 1 / by Pierre Élie Félix Perrédès. Source: Wellcome Collection.

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    and S. nigricans, for example—the advantage is on the side of the pericyclic fibres. As it is important to be able to distin¬ guish the pericyclic fibres from those of the secondary bast, it will be necessary to consider both of them here, although the consideration of the bast fibres belongs more properly to the next section. Both are usually polygonal in transverse section, but the pericyclic fibres frequently possess a ten¬ dency to become rounded at the corners and elongated in a tangential direction. In Populus the fibres of the bast never exhibit sharp striae, whereas those of the pericycle generally do—compare Fig. 16 with Figs. 17, 19, 20, etc., on this point: the finer concentric lines which I have drawn in Fig. 18 are somewhat hypothetical, and were introduced mainly as shading; finding that they might tend to mislead, I have omitted them from all subsequent sketches. In Salix, in the large majority of cases, both sets of fibres exhibit very distinct striations; so very sharp, indeed, are these in many instances that they present the appearance of deep grooves formed by an etching needle. The striations are frequently finer and more numerous in the pericyclic than in the bast fibres, but exceptions occur which will be considered in detail later on. In both genera the fibres of the pericycle, with few exceptions, react much less strongly with phloroglucin and hydrochloric acid than those of the bast—a feature which usually affords a ready means of identincation. The “ middle lamella ” is everywhere the most lignified part of the fibres, and is uniformly relatively thin in the bast fibres of the poplars, but subject to variations elsewhere. The groups of fibres in the bast are beset with sacs containing prismatic crystals of calcium oxalate, whereas these sacs usually occur but sparingly in connection with the groups of the pericycle. This factor is, no doubt, responsible to some extent for the darker appearance which a fibrous group of the bast presents after treatment with phloroglucin and hydrochloric acid, inasmuch as the crystals in the sacs are enclosed in an envelope—said by Pfitzer (de Bary, p. 140) and by Moeller (p. 92) to consist of cellulose (!)—which is very deeply stained by that reagent. By means of a combination of the above factors it is nearly always possible to distinguish the pericyclic fibres from those of the bast, for although one or more of these factors may not hold good in individual cases, the residue of them is usually ample to settle the question. The groups of pericyclic fibres may or may not become broken up as the bark increases in thickness, but in the
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