F. serratus cc The frond coriaceous, flat, mid-ribbed, linear, dichotomous, serrated at the margins; receptacles solitary, terminal, flat, linear, serrated, sharpish." It is sometimes call black wrack, or prickly tang, sometimes simply ware. It is distinguished at first sight by the edges being serrated, and by the absence of air-vesicles. It is only uncovered at ebb tide, growing, as already remarked, in deeper water than F. vesiculosus, or nodosus. In its mode of growth, it forms a pulvillum or circular tuft, spread ing out on every side from a central point olattachment. When fresh, the frond is of a dark olive green colour ; when cast ashore and dried on the beach, it is almost black. It is very frequently overrun by the small coralline, called Sertularia pumila, or sea-tamarisk. Serpula spirorbis, and spirillum, are also frequent on it. The black wrack is preferred for covering lobsters, or other shell-fish, that are to be kept alive during land carriage, being less apt to run into fermentation than some others which abound with mucus. According to Gmelin, 6 ounces only of lixivial salt are procured from 16 ounces of the ashes; and Turner mentions, that he was told that it is but little used for making kelp in the Western Islands, " because it shrinks so much in drying, and contains so little marine salt," meaning soda. In Norway, it is called bred tang ; and Gunner states, that in some parts of that country, the in habitants sprinkle it over with meal, and give it to their cattle.
F. loreus: " The substance of the frond is between car tilaginous and coriaceous, compressed, linear, nerveless, entire at the margins, dichotomous, expanded at its base into a bell-shaped cup ; tubercles immersed in every part, and on both sides of the frond." This species is well known by the name of sea-thongs. In Orkney it is called drew a name which would seem to be etymologically related to the badreux of the Straits of Magellan. It is pretty com mon in the north of Scotland and its islands, particularly on shelving sandstone rocks. When in a young state, be fore the thongs have grown, it forms a concave disc or cup, and gives to the rocks the appearance of being covered with some sort of mushroom, or rather pcziza, as men tioned in the specific character. From this circumstance, it is described by sonic old wriic rs as Furus fisngis affi nis ; and it is perhaps the Fungus phasganoides of others. The extended st•ap-shaped fronds, genel any two in num ber, arise from the centre of the cup. They are dichoto mous, or divide into two at intervals They are generally three, often six, or even ten feet in length. Borlase, indeed, in his History of Cornwall, mentions, that on that coast they are sometimes found twenty feet long. The colour is olive green, with a tinge of brown. The plant is pulpy and succulent, and a good deal of excellent kelp is made from it in Orkney ; for instance in the island of \Vestray, on an estate belonging to Dr Traill of Liverpool It is a perennial species, or at least the plants require two years to come to perfection. \Vahlenberg therefore is in a mis take when he says that it is an annual, but it must he con sidered, that he describes from observations made on the most stormy shores of Norway, where, as he tells us, not a vestige of it survives the winter, where the discs appear only in May, and where the plant never attains a greater length than eight or twelve inches. The same author
gives it as his opinion, that the cup-shaped disc is the only part analogous to a frond, the thongs being merely semi niferous spikes. To this notion he has been led, partly by the imperfect growth of the specimens lie was acquainted with, and perhaps partly by the inaccurate description of the fructification given by Dr Roth. This was first cor rectly described and delineated by Mr Turner, (Hist. Fuc. t. 196.) Elliptical tubercles are every where immersed through the strap shaped fronds, containing masses of ini• nute dark brown seeds.
F. Pam: " The frond cartilaginous, slimy, cylindrical, filiform, attenuated at both ends, jointed internally, spirally twisted when old." This species is frequently called .sea lace. In Orkney, it gets the name of catgut, and in Shet land lucky nzinny's lines. The length to which it grows is amazing, not less than from twenty to forty feet. Light foot mentions, that the stalks, skinned when half dry and twisted, acquire such strength and toughness, as to he used for fishing line, like Indian grass, (which last, although it has got this vegetable name, is an animal substance, attach ed to the ovaries of some of the small foreign sharks.) The plant consists of a simple frond, without branches. It is of a deep olive colour. In the interior, the stem is divided by horizontal partitions, which Lamouroux says form a spiral when the plant becomes bent or twisted. The Bi shop of Carlisle, and Mr Woodward, had previously re marked (in Lin. Trans. vol. iii.) that the whole frond is composed of two equal longitudinal threads, coiled spirally round each other ; this structure becoming evident when the plant has received an injury. It floats about in the man ner of Sparganium natans, following the course of the waves; but, as remarked by Lionxus, it lies immediately under the surface of the water, not on it. In Scalpa Bay, near Kirk wall in Orkney, we have sailed through meadows of it in a pinnace, not without some difficulty, where the water was between three and four fathoms deep, and where of course the waving weeds most at least have been from twenty to thirty feet long. This, too, was the growth of one season ; for the storms of winter completely sweep it from the bay every season. The plant, however, may not, strictly speaking, be an annual ; and Lamouroux observes, that its duration depends very much on the nature of the place where it grows. in Oi kney, a considerable quantity of kelp is occasionally made from this species ; and the kelp makers remark, that " it falls small in burning, and wash es like soap."; It is common in all the friths of Norway, as far as the North Cape; and Bishop Gunner adds, that it furnishes a grateful and nutritious food to the Norwegian cattle. The fructification of this species has long been a problem to the naturalist. Roth considered it as placed in a glandular capsule, at the extremity of the plant. Stack house thought he found it hid in the substance of the plant in the form of naked grains. Lamouroux is of opinion, that it is to be sought in certain tubercular excrescences, sometimes to be observed near the base or root of the plant. Turner has lately ascertained, that the seeds, or pernaps capsules containing seeds, are situated in the substance of the frond ; that they are of a pyrilorm shape, and crowded together ; and that they escape as the epidermis melts away.