An analysis of the British ferns and their allies / By G.W. Francis.

  • George William Francis
Date:
1842
Catalogue details

Licence: Public Domain Mark

Credit: An analysis of the British ferns and their allies / By G.W. Francis. Source: Wellcome Collection.

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    The Scales so visible upon some species, have been thought merely an excrescent growth caused by superabundant sap exuding from the surcharged pores. Sprengel supposed that they wrere part of the epidermis itself, lacerated by the pressure of the juices beneath. Perhaps both of these opinions are correct, a part of the epidermis of the frond being first detached, and afterwards nourished in the same manner as animal hair, and although void of life yet increasing from the base. The Cuticle of the leafy portion of the frond presents a reticulated appear- ance, (the meshes having wavy sides,) and is furnished on the under surface with respiratory stomata, similar in form and function to those of Flowering Plants. The number of these on a given space is in a great degree accordant with the rapidity of the frond’s withering when gathered. They are very abun- dant in Aspidium filix-foemina, Aspidium dilatatum, and Polypodium Dryopteris. Thus is explained the cause of the drooping habit of this last and some other species. Be it observed, however, that in Grammitis ceterach and Aspidium lobatum they are still more numerous, yet these latter plants do not wither so soon, a circumstance that may easily be accounted for from the frond of both being thicker, the deprivation of an equal quantity of water not producing so great an effect. THE REPRODUCTION of Ferns is a subject involved in much obscurity. Hedwig, Bernhardi, and others, have proposed theories to explain this intricate matter, but without success. That the Ferns have no visible flowers is evident, but that they have some apparatus analogous to stamens, is maintained by most of our first botanists. So keen has been the search for these in the present tribe, that every part of the plant has been subjected to the minutest investigation : not only the theca;, their ring, and their cover, but the spiral vessels of the rachis, the stomata upon their cuticle, and the glands which are sometimes found attending upon them. Sprengel long ago stated that the young sori, or rather that the swelled extre- mity of the veins of Polypodium vulgare, which sometimes remain abortive, and at others produce thecse, were filled with oblong-shaped bodies of a greyish color, which he considered to be stamens, and as yielding pollen in the same manner as the external stamens of flowering plants. These being attended upon by young ovules, the latter became impregnated and grew to perfection, while the pollen masses were decayed or absorbed. This opinion was in a great degree and for a long time disregarded, (perhaps because of his imperfect figures,) and the grey bodies considered to be abortive capsules. The following remark, however, from “ The Annals of Natural History,” given in the synopsis of a paper read before the Academy of Sciences at Bei’lin, March, 1840, by Professor Link, throws a stronger light upon the subject. “ The part which Sprengel years ago indistinctly figured, and which Blume and Presl at present consider to be made organs of fructification, have been more accurately examined by Professor Link, and illus- trated by drawings. They are long hollow filaments, separated by septa into articulations generally simple, rarely ramified; the last articulation is thicker,
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