Sect. (I.) With petiolated air-vesicles; leaves distinct, .either sessile or petiolated. This includes F. natans and F. bacciferus of Turner, (t. 46, 47.) both of them found floating in the ocean, and forming much of the Mar do Sargasso of the Portuguese. But not one British species falls under this section, unless, perhaps, F. salicifolius of Poiret.
(2.) With petiolated air-vesicles, furnished with a ter minal foliaceous membrane ; as F. turbinatus, (Turn. t. 24.) found in the East and West Indies.
(3.) With oblong vesicles, winged with a triple mem brane, producing a three-sided or angular appearance. A single species only belongs to this section, viz. F. triqueter, (Turn. t. 34.) from the sea near the Cape.
(4.) With petiolated vesicles lengthening in the form of a pod. Highly characteristic of this section, a Nvell known British species occurs, F. siliquosus ; but the vesicles or air-bladders may be readily overlooked by a careless ob server, on account of their resemblance to the receptacles generally to be found on the same plant.
(5.) The vesicles forming a pal t of the branches ; leaves distinct. For example, F. tamariscifolius of Hudson, (F. ericoides, Turn. t. 191.) (6.) Fructification at the ends of the fronds, which are flat, branched, generally provided with a single nerve, and with vesicles. This includes the two very abundant and well known species, F. vesiculosus and serratus.
(7.) Vesicles innate in the branches ; the fructification on peduncles. This likewise includes a very general spe cies, F. nodosus.
(8.) Without leaves ; vesicles like a string of beads, and covered with the fructification. This section is created solely for the very remarkable sea-weed named by Labil lardiere F. moniliformis, and by Nlr Turner F. Banksii, (Hist. Rue. t. 1.) The former name is so expressive of the character of the plant, that any change is to be deprecated, particularly as the illustrious President of the Royal Socie ty is already loaded with well merited botanical honours.
(9.) Without vesicles, and with a single round umbilica ted frond at the base of the branches —This section em braces only the remarkable species F. loreus, common on many of our shores, and which attacts attention chiefly on account of the round umbilicated frond above mentioned, which, in the early stage of growth, resembles a large pe ziza, and gives the rocks the appearance of being covered with a crop of mushrooms.
(10.) Without leaves and without vesicles ; fructification at the ends of the branches, which are channelled.—This takes in F. canaliculatus (Turn. t. 3.), common on our shores; and F. Mackaii (t. 52.), a species found on the west coast of Scotland, and named in honour of the discoverer Mr James Townsend Mackay, of the College Botanic Gar den, Dublin, an excellent and most deserving botanist.
(I I.) Without leaves or vesicles ; branches cylindrical, with the fructification at the tips; as F. tuberculatns, (Turn. t. 7.) 2. Lanzinaria : " With the root fibrous and branched." This generic character is perhaps objectionable, on the groupd that the root is frequently wanting in specimens of sea-weeds which are cast ashore; but, on the other hand, the fructification, from which generic characters are com monly taken, is also frequently wanting, and at any rate it is very little known. Most of the laminarix are large plants, with broad fronds, inhabiting deep places of the shores, where they are much exposed to the action of waves, and requiring therefore the strong mode of attach ment with which they are furnished, and from which the generic character is derived. Some have air-vesicles, as F. pyriferus (Turn. t. 110.), and F. buccinalis (t. 139.); and in others, vesicles seem entirely wanting. Not only the gi gantic sea-weeds of the Southern Seas, some of them de scribed as more than 1000 feet in length, belong to this ge nus; the largest of the British fuci also fall under it, the well known great tangles, F. polyschides or bulbosus, F. digitatus and saccharinus.
3. Osmundaria : Fructifications minute, oblong, on footstalks, situated at the points of the leaves; the leaves entirely covered with small spiny mamillx."—This genus, named from its resemblance to some ferns of the genus Osmunda, is formed for the sake of one species of trifling size, brought from the shores or New I Tolland. Till, how ever, it be examined by some botanist in a recent state, its characters cannot be accurately known.