B F E A, B, C. Plants of Gigartina Helminthocorton, natural size. (260.) Spongiocarpacea and Furcellacea. The genera Polyides, or sea wort-reet, and Furcellaria, or sea fork-let, each consisting of but one known species, mark the transition by their structure from the Florine to the Fucina; and although of each there is but one known species, yet so different are they from each other and from the rest of the Algae, that both genera have been very properly separated by Greville and made typical of independent groups, the first being called Spongiocarpacea, and the second, Furcellaceæ, [§ 262, fig. c, D.] (261.) Spongiocarpacea. The colour, habit, and general structure, indicate the affinity of the Spongiocarpacea with the Floracea, but the naked spongy wort-like sori of Polyides, formed by clusters of wedge-shaped sporidia intermixed with radiating filaments, at once distinguish it from that, as well as from all other sections, [vide § 262, fig. D.] (262.) The Furcellacea are likewise as well distinguished; for, P c. Furcellaria lumbricalis. (g) Entire plant. (h) Fructification in apex of frond. (i) Longitudinal section of ditto. section. (k) Spores. D. Polyoides rotundus. (j) Horizontal (1) Plant with Fructification. (m) Apex with fruit removed. (n) Transverse section. (0) Spores. (p) Sporidia mixed with fibres. although the appearance of Furcellaria [vide fig. c.] is something approaching to the Fucine, and although like them it is of a less brilliant colour than most of the Florine, and becomes darker on exposure to the atmosphere, still its fronds are not fibrous; and its terminal conceptacles, with horizontal circular strata of dark oblong-pearshaped spores, will distinguish it sufficiently from the beforenamed sections. (263.) Collectively, the types Furcellacea, Spongiocarpacea, Floracea, Thaumacea, Gastrocarpacea, and Caulerpacea, form the extensive section Florine, which with Fucine immediately to be described, and Ulvine previously examined, constitute an order sometimes called pre-eminently Algae, sometimes Phyce, sometimes Thalassiophytes, or Thalassiophycæ, but for which, a word either compounded of the two most important sections, types, and genera, or derived from one of them, would be a preferable name, [§ 289.] FUCINE. (264.) DICTYOTACEE. The sea networks, forming the first type of this section, are well characterised by the beautifully reticulated texture of the tegument, whence indeed the name Dictyotacea, which has been given to the group, from its normal genus Dictyota. The fronds are of various forms, but in all, excepting Halyseris, the sea-endive, ribless; and the conceptacles are pellucid, inclosing the sporules, which are for the most part produced beneath the epenchyme. (265.) The Peacock's tail, or Padina pavonia, affords a beautiful example of this section; but Chorda filum, sea-whiplash, or (a) Chorda Filum. (6) Portion of frond artificially unrolled to shew its spiral structure. (c) Spores magnified. (d) Portion in fructification. (e) Section, to shew internal structure. sea-catgut, is perhaps a more familiar instance. This plant is often found thirty or forty feet in length, and Lightfoot says, the Highlanders twist it, when skinned, into fishing lines. And so abundantly does it sometimes grow that, as Mr. Neill declares, it is with difficulty a pinnace can make its way through oceanic meadows of this weed. The frond of this cord-like flag is hollow within, and the channel interrupted at short distances by transverse partitions, the use of which, according to Colonel Stackhouse, is to confine the air, or elastic vapour, to certain spaces; so as to act like swimming bladders and increase the buoyancy of the plant, which extends itself to such an amazing length, and always shoots upwards to the surface. (266.) The smell of (Halyseris) the sea-endive, the only genus with a ribbed frond, is said to be, "when fresh gathered, extremely powerful and disagreeable." (267.) Chorduriacea. The Chordaria, or sea-whipcord, which differs from all other Alge by its solid filiform cylindrical frond, even although the fructification is very imperfectly known, has been arranged in a separate section by Greville, who thinks," its singular structure removes it from all the other orders;" and hence it is the only known example of the Chordariacea, or twinewracks. A. Macrocystis pyrifera. B. Laminaria buccinalis. (a) Transverse section of stem. (b) A portion magnified to shew structure. c. Chordaria flagelliformis. (c) Transverse section of frond with fruit. (d) Fibres and sporidia. (e) Spores still further magnified. (f) Longitudinal section of frond magnified with one of the fibres. (268.) Sporochnacea. Another type of this section, the Sporochnacea, which contains the genera Sporochnus, or scatter-tuft, с (a) Sporochnus pedunculatus, natural size. (b) A receptacle terminated by its tuft of filaments. (c) Section of the receptacle. (d) Filaments with their fertile summits. (e) Portion of a filament of the receptacle. Dichloria, or changeling, and a genus named in honour of Desmarest, Desmarestia or Desmia, is chiefly characterized by bearing little tufts of fine green filaments on the fronds, but which are deciduous in some, and not yet observed in all the species. The fructification is collected in tubercles, either stalked or sessile. These plants, which are all marine, and of an olive or yellowish green colour, although they do not change to black in drying, become flaccid on exposure to air, acquiring a verdigris colour, and then possess the curious property of rapidly decomposing other delicate Algae in contact with them.-Grev. (269.) The sea-belts, or sea-girdles (Laminaria), the murlins, honey-ware, or bladder-locks (Alaria), with the interminable (Macrocystis), [§ 267, fig. A.], or bladder-thread, form, with a few other allied genera, such as Durvillæa, Lessonia, and so forth, a very natural and well-marked type, called, from their flattened form, and from Laminaria, or tangle, the name of the normal genus, Laminaceae, or tangle-wracks; by Bory St. Vincent and Greville they are denominated Laminariea; this termination, however, as in the other cases where a similar alteration has been made, is only changed from the manifest expediency of designating similar grades of analysis by somewhat similar words. |