FILICES, OR FERNS, the great natural series of plants included with the Musci, Hepatica., Liclienes, Confery r, Ste. in the CRYP •OGA:MIA of Linnaeus, and ACOTYLEDONES of Jussieu. The writers on these •plants have differed widely in their opinions as to the etymology of the word slices. Ains worth derives fills, the name used by Pliny, from jilum quasi filatinz incisce; but Ainsworth was no naturalist : even the roots of these plants have no more resemblance tofi/um, " a thread," than those of other plants. It seems far more probable that the latter name is derived a MO ?WY PJAACJV ; the leaves or fronds of the European ferns being alone visible, as the stems and roots are either hid under ground, or decayed leaves, mosses,'&c.
In describing the peculiarities in the structure of the embryo and manner of germinating of the seeds of these plants, it is necessary, for the sake of perspicuity, to pre sent a general comparative view of the analogous parts of the embryo in dicotyledonous plants. For, as to the sup posed morincotyledoues, it will scarcely be credited, that in them naturalists have not hitherto determined with pre cision, to which part of the embryo the term cotyledon ought with propriety to be applied. In fact, there is every reason to conclude, that no organ whatever, strictly analo gous with the true cot) ledon, exists in the seeds of the hi thereto supposed monocotyledonous series; although all of them are, independent of this, sufficiently distinguished by the peculiarities of their respective organization. It is therefore in the seed-lobes of the well known dicotyledones, that we find the true types of the real cotyledons; and, by comparing these with the organs of the embryo in other germinating seeds, and especially observing the purposes to which they are destined in the economy of this interest ing process, that we are enabled to determine, with accu racy, their true nature. It was with this view that the ex periments of Lindsay, who, it will be recollected, first called the attention of naturalists to the germination of ferns,* were lately repeated by the author of the present observations.
Gxrtner, to whom the greatest obligation is due in many respects, has denied the existence of cotyledons in these plants, asserting that the testa of the seed is in them, as well as in those of Musci and Fuci, totally occupied with vitellus, an organ to which he has ascribed a distinct cha racter. Lindsay has described this part as appearing of
an irregular form ; which is indeed sufficiently expressed in his Figures (8. 9. 10. 11. Pl. II.) ut supra. But, after repeated observations on the germinating seeds of various genera, this supposed irregularity has never once occurred to us; indeed, anomalies of this kind, so far as we know, never do occur in the figure of the embryo, in tile same natural series ; in which, with certain shades of difference, the characteristic structure of the kindred tribes invariably exists. Without, however, impeaching the accuracy of Lindsay, may not the evident incongruity of his figures with each other be explained, by supposing the engravings to have been executed during his absence in the West In dies, from which the original drawings, now in the posses sion of lir Wright of Edinburgh, were sent Erhart, whose observations were made on two species of Aspidium and one ?tliyrizan only, coincides with Lind say in repreariting but one lobe in the embryo.* But the figure of theTmbryo, as observed by Sprcngcl, is describ ed with much more accuracy than by either of these wri ters, although he had au opportunity of seeing only a sin gle species, the .4thyrium filix fcrnaina, in a state of spon taneous germination.t Having, however, had the good fortune to observe, from its commencement, the germina ting process, in several species belonging to genera so clearly distinct, that they must be considered as belonging to different tribes, namely, the Polyitodiacea., and Pteridem; and having traced the embryo from becom ing visible as a point, to its gradual expansion and final evolution IP a perfect plant, we have succeeded so far in determining with precision the figure and man ner of growth of their various organs, which are here deli neated by the accurate pencil of Mr Syme, during what may be termed the first and second periods of the exis tence of this singular race.