On the forms and structure of fern-stems / by George Ogilvie.

  • Ogilvie, George
Date:
1859
Catalogue details

Licence: Public Domain Mark

Credit: On the forms and structure of fern-stems / by George Ogilvie. Source: Wellcome Collection.

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    As examples of this form of caudex may be mentioned Lastrea Filix mas, L. dilatata, L. cristata, Polystichum aculeatum, and P. Lonchitis. The other form of caudex is intermediate between this last variety and the stoloniferous rhizome first described; for the axis branches so repeatedly in a dichotomous manner, by the duplication of its terminal buds, that, when dissected out, it has somewhat the character of the stoloniferous rhizome; but in its natural state it is so thickly set both with foot-stalks and root¬ lets, that nothing is to be distinguished but a mass of tangled roots, more or less tufted above and densely fibrous below. A caudex of one kind or other occurs in all our larger Ferns except Pteris aquilina, and in the majority it appears to be branched. So at least it is in Allosurus crispus, Blechnum horeale, Osmunda regalis, Lastrea Oreopteris, and in Filix foemina and the genus Asplenium generally. (PI. VIII. fig. 3; IX. figs. 4, 5, 6.) It is doubtful if the branched caudex ever becomes arbores¬ cent as a normal occurrence*. Branched Tree-ferns are cer¬ tainly met with, but rather, it would seem, as an occasional abnormality than as a regular form. Among our native Ferns, Ophioglossum and Botrychium are remarkable for their vernation being straight, not circinate, as in the rest of the group, and the last-mentioned species also for the edges of the solitary petiole cohering, so as to embrace the point of the axis and form a cavity which lodges the embryo of the next yeaPs frond; within its petiole the rudiments of the frond of the succeeding year may in like manner be detected. The stem itself may probably be considered a modification of the simple caudex. Among the Fern-allies of our flora, the stoloniferous is the most common form of stem. In Equisetacese it is subterranean, like that of the Ferns; but in Pilularia and Lycopodium it creeps along the surface of the ground. In the larger species of Lycopodium the successive stages of annual growth, and the separation of the shoots as independent plants by the gradual decay of the older portion of the stem, are more clearly brought out than even in the stoloniferous roots of Ferns. In Isoetes we have a peculiarly modified form of the simple caudex. Internal Structure of Fern-stems. The next point to be noticed is the internal structure of the vegetative axis of the Fern, principally as it atfects the disposi- * An analogical argument in favour of this may be drawn from Palm- stems, which are normally simple from the development of a single terminal bud, but which are branched in a few^ species, as Phoenix, or form lateral buds, as in Areca, Caryota, and Chamcerops.
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