5th, all'odu/aria or Knob-weed : 46 Herbacca, viridia, ra mis alternis, capillaceis, nodosis. Fr. Tubercula ramos per intervalla occtipantia." This is divided into sections, with simple filiform fronds, as Conferva plicata of Hudson, and with filiform fronds much branched, as C. glomerata.
6th, Catenaria or Chain-weed: Gelatinosa, ramosa, ar ticulata ; articulis tumidis." The fructification was un known to the author. The genus was divided into several sections, with vet'ticillate, opposite, dichotomous, and al ternate branches, and included Ulva articulata of Hudson, Conferva corallinoides of Linnaeus, and similar plants.
7th, Fucus or Wrack : cc Coriaccus, dichotomus, costa tus. Fr. Vesiculx terminales, intus gelatinosx, tuberculis seminalibus rotundis." This is divided into sections; with air-bladders, as F. vcsiculosus; without air-bladders, as F. serratus, (Turn. t. 90,) : and with inflated fronds, as F. in flatus of Linnaeus, now ascertained to be a variety only of F. vesiculosus.
8th, Platyceros : " Palmatus, dichotomus, enervius. Fr. Vesicul2e ficialcs, sessiles, sparsx, subglobosm." This is subdivided into leathery, nembranaceous, and gelatinous. and, according to Dr Walker, embraces F. ceranoides and lacerus of Linnaeus.
9th, Phasganon or Tangle : Stipitatum, monophyllum, coriaceum. Fr. Vesiculve superficiales globosa., gelati nom, inter corticem et epidermidem folii tumidx." This is subdivided into two sections ; those which are nerveless or destitute of a midrib, and those which have a midrib. The former section includes Ph. balteiforme, or Sea-belt of Dr Walker, (F. saccharinus, Lin.); Ph. Marine or St Mary's thistle, Walk. (F. polyschides, Lightf.); and Ph. esculeri tum, or Comman tang, Walk. (F. digitatus, Lin.) The latter section includes Ph. Scoticum, Walk. or F. esculen tus, Lin.
loth, U/va, or Laver : Sessilis, monophylla, membra nacea, enervia. Fr. Tubereula infra mcmbranas, Lin." There are three sections, by means of which plants very widely different are brought together : (1.) Frondescent, including U. umbilicalis, or slake ; (2.) completely tubu lar, such as the common U. compressa ; and (3.) tubu lar, divided by septa., embracing F. filurn of Linnaeus, af terwards described (Turn. t. 86).
1 I th, Chartacea, or Dilse : 44 Sessilis, monophylla, ener via, palmata, laciniata." The fructification was unknown to Dr Walker. There are two sections ; membranaceous and gelatinous. The first includes the common dilse, F. palmatus (Turn. t. 115.), with F. proffer, (Lightf. t. 30.)
and others; second, F. gelatinosus of Hudson, the Sea ragged staff of Pallas, 353. It may be observed, that Fo cus Sarniensis of Roth, (Turn. t. 44.) was known to Dr Walker by the name of Chartacea dichotoma.
12th, Plumarium, or Feather•weed : Stipitatum, carti lagincum, inarticulatum, ramosum, pennatum ; fronde com posite. Fr. Globuli latcrales sessiles." This genus is di vided into several sections, being cartilaginous or membra naceous, and possessing or wanting a midrib ; and includes F. plumosus, (Turn. t. 60.) dcntatus, (t. 13.) and others.
13th, Xeurophyllunz, or Nerve-weed : Stipitatum, ra mosuni; foliis membranaccis distinctis. Fr. Tubercula globosa pedunculata, superficie foliorum. F. sanguineus is a good example of this genus, (Turn. t. 36.) Spongia is the last genus of Dr 1Valker ; and he divides sponges into sessile and branched ; but it is now generally admitted that they belong to the animal, and not to the ve getable kingdom.
Mr Stackhouse's Method.
Mr Stackhousc published his arrangement, in his .Vereis Britannica, about the year 1797. He formed six genera: Fucus, Palmaria, Chondrus, Sphmrococcus, Corda, and Codium ; the characters of which are taken chiefly from the fructification, but partly from structure.
1. Farms has this generic character: " Fructification a jelly-like mass, with imbedded seed-bearing. granules, and external conical papilla., terminating." This genus is di vided into two sections : with the fruit exserted, as F. ser ratus and vesiculosus ; or innate, as F. loreus, (Turn. t. 196.) 2. Palmaria. 66 Skin smooth, glossy, polished on each side, with a colourless mucus within ; forming together a thick consistent substance, with the seeds very minute, na ked, orbicular, of the colour of the skin of the plant, dis posed in patches or in lines, jest within the surface of the cuticle." This includes F. digitatus, (Turn. t. 162.) and (t. 114.) 3. Chondrus. " Fructification an ovate rigid imbedded pericarp, containing seeds in a clear mucus, and promi nent on either surface." This embraces only one species, F. crisp's, and its numerous varieties. (Turn. t. 216, 217.) 4. Splicerococcus." Fructification, external globular pe ricarps, adnate or immersed ; sessile or pedunculate ; con taining seeds as in the others." This genus is subdivided into several sections ; with distinct leaves, as F. sangui neus ; with a midrib, as F. alatus, (Turn. t. 1 60.); with a compressed frond, as F. coccineus; or a round frond, as 1'. otundus.