Comparative anatomy of the barks of the Salicaceae. Pt. I / 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. I / by Pierre Élie Félix Perrédès. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    periderm, which originates from the phelloderm, if such it be, is terminated in the same way by a similar layer of stone cells, so that the periderm of an older piece of bark exhibits a more or less concentric series of sclerenchymatous layers (sc. 1., Fig. 7). The outer layers of the periderm, however, show a strong tendency to exfoliate, and the last-formed layer of stone cells is sometimes exposed. The cork cells of young poplar twigs are nearly isodia- metric, or somewhat elongated radially (k., Figs. 2. 3, and 6), in older barks they usually present the customary flattened and tangentially elongated outline (k., Figs. 5 and 8) ; the extent to which tangential elongation occurs may vary some- what, however, even in the same section, and is generally least pronounced where the production of cork is vigorous. These periderms consist, with few exceptions, of thin-walled suberised cells: in P. deltoides and P. pyramidalis I have occasionally observed tangential bands of thickened cells (sc., Fig. 8) and more examples of this could, doubtless, be found, especially in cases where the periderm is copiously developed ; but it is only in P. Fremonti that the regular formation of bands of thickened cells becomes (apparently) a fixed and constant feature.1 In all these cases the thickened portions of such cells are, without exception, lignified, while the region of thickening extends uniformly around the whole cell; the latter point is, nevertheless, subject to many fluc- tuations. The amount of phelloderm formed in Populus is always slight. With the one exception of P. Fremonti, the periderms of the poplars do not afford any characters of much diagnostic value, although the relative thicknesses of the periderms as a whole, in different species, may be of some importance in extreme cases : thus the covering of periderm in P. tremuloides and P. grandidentata (Figs. 28 and 30) is almost invariably thin, while in P. angustifolia and P. pyra- midalis (Figs. 34 and 36) it is thick, sometimes excessively so. l It is, of course, possible that this peculiarity may be dependent upon ecological factors, and as I have only examined specimens from one locality (San Bernardino, S. California), the particulars of the latter, which were very kindly furnished by Mr. S. B. Parish, of S. Bernardino, Cal., are herewith appended:—“ Specimens from a tree about 2J ft. in diameter, about 40 ft. high, and nct]over thirty years old. Growing in loamy soil which is naturally somewhat damp, and contains a noticeable percentage of alkali, as indicated by the growth of Distichlis maritima and Baccharis Emeryi.”