GENERAL ARRANGEMENT OF FERNS.
Previous to the excellent paper of Dr now Sir James Edward Smith, published in the fifth volume of the Me moirs of the Academy of Sciences at Turin, our knowledge of the genera was very imperfect ; but this celebrated gbtanist, by a more accurate examination of the species, was enabled to reform the genera, and to reduce them, from a state of comparative confusion, nearly to their present form. Since the work of Smith, others have followed on the same principle ; and Bernhardi, Swartz, and Sprengel, have respectively contributed to our stock of knowledge of these plants.
The general principles on which the genera are at pre sent distinguished, consist in the folm, attachment, and manner of opening of the involucrum ; and when this en velope is wanting, in the manner in which the sori (groups) are arranged on the receptacle of the frond. To the re ceptacle, the capsules are generally attached by a fruit stalk, in some so short, as to cause them to appear sessile ; in others of a considerable length, and sometimes branch ed with a capsule on each division. The receptacle, whe ther situated on the plane of the frond, or 'elevated above it, is in by far the greater number of known genera com mon to a numerous group of capsules, although, as will soon appear, there are instances of single multilocular seed-vessels apparently sessile in the frond itself. The capsules in most cf the tribes are girt with a ring, which, on the maturity of the seeds, breaks, and springing back wards, ejects them with considerable force to some dis tance from the plant. This circumstance may be observ ed occasionally, by placing the ripened groups under the microscope, with a sheet of writing paper under them to receive the exploded seeds. In a great part of the series, many of the genera want the rings ; but, instead of them, their capsules are more or less marked with strix, in the direction of which they burst.
An attempt is here made to arrange the genera on the principle of the natural method, as far as our limited knowledge of the structure of their most essential organs would admit. It is no doubt very likely, that several of
those we have ventured to approximate, will be found de ficient in affinity by subsequent observers ; but as an ad herence to truth and nature is the great object, this will only add to our satisfaction ; conscious, as the illustrious Jussieu observes, that such errors originate " Non legum naturalium, sed pravze eorum interpretationis, vitio." Linnxus referred the only species knov,n to him to As plenium, the oblong, single seed-vessels somewhat resem bling the groups of capsules in that genus, when superfi cially observed. There is a good figure of the generic character in the Annals of Botany,ii. Pl. 10. Three spe cies are described by IVilldenow, all natives of America, viz. the D. simplicifolia, (Runge, Pl. Cujan. tab. 136.) D. rosa, (Plum. Pl. American. tab. 6.) and D. alata, (Plum. Ell. tab. 109.) The genera of this tribe approach much nearer to the majority of the series than the last. The seeds are con tained in minute capsules arranged in groups, and are unilocular, striated,and sessile. The strict are traniverse or oblique, and the capsules burst longitudinally in the direc tion of the stiiar. The groups are naked, and, except in Mertensia, have a very limited number of capsules.
(I.) Angiopteris, (WilId. 1944.) Capsules elliptical, disposed in groups of five or seven, in double rows, along the secondary veins of the frond, and opening longitudinally.
There is but one solitary species, the A. evecta, hitherto known, figured by Hoffman, (Comm. Gat. p. 29. tab. 5.) This species was brought from the islands of the South Sea by Forster ; and Swartz has represented the generic character in the Annals. of Botany, Pl. 10. fig. 4. This species is five feet in height, and has the aspect of a small palm.