in the different species of Griffithsia.

We see them enlarge for a certain space of

time, and present the appearance of a rose-coloured globule; but at a more advanced period the external envelope dilates, becomes transparent, and the central body, considerably increased in size, tends to separate into four parts or distinct spores, each invested with a special envelope, and of the most brilliant carmine colour. This structure brings to mind, with some slight differences, that of pollen grains." And then M. Decaisne goes on to explain how, by a stoppage of growth, or by interior multiplication, the quaternary character of these bodies may be affected.

According to Endlicher, the maximum of this order is found in the ocean between 35° and 48° N. lat. They are entirely marine. Towards the pole and the equator they diminish in numbers, and are comparatively rare in the southern hemisphere. Rhododermis Drummondi covers the rocks of caves with patches of a dark blood or brickred colour.

It is among the genera of this order that occur the seaweeds whose gelatinous qualities render them valuable as food. Many species are so used among Indian nations. Of them Plocaria tenax, and candida, are the principal; and the material out of which the swallows construct the esculent nests which are so highly valued by the Chinese, is supposed to be a sort of Gelidium. The British Plocaria compressa, and Chondrus crispus (or Carrageen moss), have been found to possess similar qualities; and another species of the order, on the south-west coast of New Holland, furnishes a jelly of great excellence. Rhodomenia palmata, the dulse of the Scots, dillesk of the Irish, and saccharine Fucus of the Icelanders, is consumed in considerable quantities throughout the maritime countries of the north of Europe, and in the Grecian Archipelago; Iridæa edulis is still occasionally used, both in Scotland and the south-west of England. Laurencia pinnatifida, distinguished for its pungency, and hence called Pepperdulse, is eaten in Scotland; and even now, though rarely, the old cry, " Buy dulse and tangle," may be heard in the streets of Edinburgh.

But it is not to mankind alone that such marine Algals have furnished luxuries, or resources in times of scarcity. Several species are greedily sought after by cattle, especially in the north of Europe. Rhodomenia palmata is so great a favourite with sheep and goats, that Bishop Gunner named it Fucus ovinus. One species is invaluable as a glue and varnish to the Chinese. This is the Plocaria tenax, the Fucus tenax of Turner's Historia Fucorum. Though a small plant, the quantity annually imported at Canton from the provinces of Fokien and Tchekiang is stated by Mr. Turner to be about 27,000 lbs. It is sold at Canton for 6d. or 8d. per pound, and is used for the purposes to which we apply glue and gum-arabic. The Chinese employ it chiefly in the manufacture of lanterns, to strengthen or varnish the paper, and sometimes to thicken or give a gloss to silks or gauze. It seems probable that this is the principal ingredient in the celebrated gummy matter called Chin-chon, or Hai-tsai, in China and Japan. Windows made merely of slips of Bamboo, crossed diagonally, have frequently their lozenge-shaped interstices wholly filled with the transparent gluten of the Hai-tsai. On the southern and western coasts of Ireland, our own Chondrus crispus is converted into size, for the use of house-painters.

In medicine we are not altogether unindebted to Rosetangles. The Plocaria Helminthochorton, or Corsican Moss, as it is frequently called, is a native of the Mediterranean, and had once a considerable reputation as a vermifuge. To Hypnea musciformis similar qualities are ascribed in the Greek Archipelago. Several species furnish Iodine, which gives them an odour of violets. Rytiphloa tinctoria yields a red dyeing matter, the Fucus of the ancients. The Plocaria candida, or Fucus amylaceus, has been found to consist of pectine, gum, and starch, with a pretty considerable quantity of inorganic matter, especially sulphate of lime. (Ch. Gaz. 1843, 638.) The Tsantjan or Kanten (called Fucus cartilaginosus), used in China as a substitute for the edible birds'-nests, seems to have a similar composition.

Suborder V. -- Sphæro-?
cocceæ. Frond cellular.

NUMBERS. GEN. 88. Sp. 682. (Endl.)

ORDER V. CHARACEE.-CHARAS.

CHARACEE, Rich in Humb. et Bonpl. N. G. Pl. 1, 45. (1815); A. Brong. in Dict. Class. 3. 474. (1823); Grev. Fl. Edin. xvii. (1824); Endlich. Gen. iv.; Schnitzl. ic.-CHARKA, Kützing, Phycologia, p. 313. DIAGNOSIS.-Tubular symmetrically branched bodies, multiplied by spiral-coated nucules, filled with starch.

Water plants composed of an axis, consisting of parallel tubes, which are either transparent or encrusted with carbonate of lime, and of regular whorls of symmetrical tubular branches. Organs of reproduction, lateral, round, succulent, brick-red globules, and axillary nucules. The globules, consisting of triangular valves, enclosing centripetal tubes and slender annular threads; the nucules having two coats, of which the external is transparent and usually surmounted by five teeth; the internal firm, spirally-ribbed, filled with starch granules of various sizes.

1

The genera of which this little order is composed are among the most obscure of the vegetable kingdom, in regard to the nature of their reproductive organs; and accordingly we find them, under the common name of Chara, placed by Linnæus among Cryptogamous plants near Lichens; then referred by the same author to Phænogamous plants, in Moncecia Monandria ; retained by Jussieu and De Candolle among Naiads, by Brown at the end of Hydrocharaceæ, and by Leman in Halorage; referred to Confervas by Von Martius, Agardh, and Wallroth; and finally admitted as a distinct order, upon the proposition of Richard, by Kunth, De Candolle, Adolphe Brongniart, Greville, Hooker, and others. Such being

Fig. XII.

3

the uncertainty about the place of these plants, it will be useful to give a rather detailed account of their structure, in which I avail myself chiefly of Ad. Brongniart's remarks in the place above referred to, and of Agardh's observations in the Ann. des Sciences, 4. 61.

Charas are aquatic plants, found in stagnant fresh or salt water; always submersed, giving out a fetid odour, and having a dull greenish colour. Their stems are regularly branched, brittle, and surrounded here and there by whorls of smaller branches. In Nitella the stem consists of a single transparent tube with transverse partitions; Agardh remarks that it is so like the tubes of some Algals, as to offer a strong proof of the affinity of the orders. In Chara, properly so called, there is, in addition to this tube, many other external ones, much smaller, which only cease to cover the central tube towards the extremities. In the axils of the uppermost whorls of these branchlets the organs of reproduction take their origin; they are of two kinds, one called the nucule, the other the globule; the former has been supposed to be the pistil, the latter the anther.

The nucule is described by Greville as being "sessile, oval, solitary, spirally striated, having a membranous covering, and the summit indistinctly cleft into five segments; the interior is filled with minute sporules. Fl. Edin. xvii. This is the general opinion entertained of its structure. But Brongniart describes it thus :-Capsule unilocular, monospermous; pericarp composed of two envelopes: the outer membranous, transparent, very thin, terminated at the upper end by five spreading

Fig. XII-1. Chara vulgaris; 2. a portion of a branch with a nucule and globule; 3. the globule more magnified; 4. the spiral tubes of the latter; 5. a nucule cut open; 6. a nucule in germination.

teeth; the inner hard, dry, opaque, formed of five narrow valves, twisted spirally." Dict. Class. I. c. He founds his opinion of the nucule containing but one germinating body upon the experiments of Vaucher, of Geneva, who ascertained that if ripe nucules of Chara, which have fallen naturally in the autumn, are kept through the winter in water, they will germinate about the end of April; at that time a little body protrudes from the upper end between the five valves, and gradually gives birth to one whorl of branches, which produce a second. Below these whorls the stem swells, and little tufts of roots are emitted. The nucule adheres for a long time to the base of the stem, even when the latter has itself begun to fructify. Hence it is reasonable to conclude that the nucule is really one-seeded. Brongniart remarks, that it is true, when a fresh nucule of Chara is cut across, an infinite number of little white grains are squeezed out; but if these were really all reproductive particles, how would they ever find their way out of the nucule, which is indehiscent? he considers them rather of the nature of albumen. And he is the more confirmed in his opinion, because in Pilularia, the thecæ of which also contain many similar grains, but one plant is produced by each theca. These grains have been ascertained by the observations of Kützing to be really starch, iodine colouring them violet; yet Endlicher describes them as spirally-striated spores. Finally, Amici has described (Ann. des Sc. 2.) the nucule in another way. He admits it to be one-seeded, but he considers the points of the five valves to be stigmata, and the valves themselves to be at once pericarp and style. These observations seem to show that the five valves of the nucule, as they are called, are a whorl of leaves, straight at first, and twisted afterwards; and that the nucule itself is analogous to the bud of flowering plants.

The globule is described by Greville as "a minute round body, of a reddish colour, composed externally of a number of triangular (always ?) scales, which separate and produce its dehiscence. The interior is filled with a mass of elastic transversely undulated filaments The scales are composed of radiating hollow tubes, partly filled with minute coloured spherical granules, which freely escape from the tubes when injured." Vaucher describes them as "tubercles formed externally of a reticulated transparent membrane, containing, in the midst of a mucilaginous fluid, certain white articulated transparent filaments, and some other cylindrical bodies, closed at one end, and appearing to open at the other. These latter are filled with the red matter to which the tubercles owe their colour, and which disappears readily and long before the maturity of the nucule." The account of the globule by Agardh is at variance with both these. "Their surface," he remarks, "is hyaline, or colourless; under this mem brane is observed a red and reticulated or cellular globe, which has not, however, always such an appearance; often, instead of this reticulated aspect, the globe is colourless, but marked by rosettes or stars, the rays of which are red or lanceolate. In the figures given by authors, one finds sometimes one of these forms, sometimes the other. I have myself found them both on the same species; and I am disposed to believe that the last state is the true kernel of the globule, concealed under the reticulated scale. (When the globule is very ripe, one may often succeed, by means of a slight degree of pressure, in separating it into several valves, as is very well shown in Wallroth's figures, tab. 2. f. 3. and tab. 5. These valves are rayed, and no doubt answer to the stars, of which mention has been made.) The kernel contains some very singular filaments; they are simple (I once thought I saw them forked), curved and interlaced, transparent and colourless, with transverse striæ, parallel and closely packed, as in an Oscillatoria or Nostoc; but what is very remarkable, they are attached, several together, to a particular organ formed like a bell, which is itself also colourless, but filled with a red pigment. This bell, to the base of which on the outside they are fixed, differs a little in form in different species. It is slender and long in Chara vulgaris, thicker in C. firma, shorter in C. delicatula, and shorter still in C. collabens. I have not succeeded in determining the exact position of these bells in the kernel. I have often thought they were the same thing as the rays of the rosettes or stars upon the globule above mentioned; whence it would follow that they are placed near the surface, while the filaments have a direction towards the centre. The bells are not numerous; they often separate from the filaments, and readily part with their pigment, which renders it difficult to observe them, and has caused them to be overlooked." That these globules, whatever their nature may be, have no resemblance in structure to anthers, is clear from these descriptions, whichever may be eventually admitted. Nevertheless Fritsche, the patient investigator of pollen, regards them as anthers ! Wallroth says he has sown them, and that they have germinated; but this observation requires to be verified.

In the annular or chambered threads of Chara are found in abundance little spiral bodies having an active motion when discharged into water, and resembling entirely the 80-called animalcules in mosses, &c. M. Thuret, who finds tentacula in the spores of Confervas, ascribes a similar moving apparatus to these bodies, adding that they are turned

brown by iodine and not dissolved by ammonia as animalcules are. (Ann. Sc. N. 2 ser. 14, 65.) They are probably analogous to the elastic spires of Equisetum.

There are two other points deserving of attention in Charas; 1st, the calcareous incrustation of some species; and 2dly, the visible and rapid motion of the sap in the articulation of the stem.

Of the genera, Nitella is transparent and free from all foreign matter; but Chara contains, on the outside of its central tube, a thick layer of calcareous matter, which renders it opaque. This incrustation appears, from the observations of Greville (Fl. Edin. 281), not to be a deposit upon the outside, and of an adventitious nature, but a result of some peculiar economy in the plant itself; and according to Brewster, it is analogous to the siliceous deposit in Equisetum, exhibiting similar phenomena.

Whatever is known of the motions of the fluids of vegetables has been necessarily a matter of inference, rather than the result of direct observation; for who could ever actually see the sap of plants move in the vessels destined to its conveyance? It is true that it was known to botanists that a certain Abbé Corti, of Lucca, had, in 1774, published some remarkable observations upon the circulation of fluid in some aquatic plants, and that the accuracy of this statement had been confirmed by Treviranus so long ago as 1817; but the fact does not seem to have attracted general attention until the publication, by Amici, the celebrated professor at Modena, of a memoir in the 18th volume of the Transactions of the Italian Society, which was succeeded by another in the 19th. From all these observers it appears, that if the stems of any transparent species of Chara, or of any opaque one, the incrustation of which is removed, are examined with a good microscope, a distinct current will be seen to take place in every tube of which the plant is composed, setting from the base to the apex of the tubes, and returning at the rate, in Chara vulgaris, of about two lines per minute (v. Ann. des Sc. 2. 51. line 9); and according to Treviranus this play is at any time destroyed by the application of a few drops of spirit, by pressure, or by any laceration of the tube. Such is the nature of the singular phenomena that are to be seen in Charas. Those who are anxious to become acquainted with the details of Amici's observations will find his first paper translated in the Annales de Chimie, 13. 384, and his second in the Ann. des Sc. 2. 41; that of Treviranus is to be found in the latter work, 10. 22. The observations made upon Chara circulation by the foregoing authors have been much extended by the careful inquiries of Solly, Slack, and Varley, whose remarks are to be found in the Transactions of the Society of Arts, vol. 49, p. 177, and vol. 50, p. 171 and by Donné, Dutrochet, and others, in the Ann. Sc. Nat. 2 ser. vol. 9, pp. 5, 65, 80, and 10, p. 346. As however they relate to physiological and not to systematical questions I forbear to dwell upon them in this place.

Fig. XII.

The creation of plants of this order would appear to have been of a very recent date, compared with that of Ferns and Palms, or even Algals, if we are to judge by their fossil remains, called Gyrogonites, which are found for the first time in the lower freshwater formation, along with numerous Dicotyledonous plants resembling those of our In the recent Flora of the world they make their appearance everywhere in stagnant waters, in Europe, Asia, and Africa, in North and South America, in New Holland, and in either India. They are most common in temperate countries.

own era.

We can scarcely claim any knowledge of their uses. Their stems, often encrusted with lime in the state of carbonate according to some, and of the phosphate according to others, are probably useful as a manure. The fetid effluvium arising from them is regarded as very unhealthy, and one of the sources of the malaria of the Campagna of Rome.

Fig. XII. A magnified view of Nitella, with the motion of its sap shown by arrows.