Part 2

With the Rhodospermeae we enter a sub-order of Algae, exclusively marine, the plants in which have always held out great attractions to the collector. In structure they are expanded or filamentous, nearly always rose-coloured or purple in colour. Of the fourteen groups into which they are divided by Harvey, the first is Ceramiaceae, articulate Algae, constituting a large proportion of the marine plants of our shores. Of the genus Ceramium, C. rubrum is the most frequent, and it is found in every latitude, almost from pole to pole. It is very variable in aspect, but can always be recognized by its fruit. C. diaphanum is a very handsome species, growing often in rock pools along with the other. There are about fifteen native species altogether, some of them rare, and all very beautiful, both as displayed on paper and seen under the microscope. Crouania attenuata is a beautiful plant, parasitic upon a Cladostephus or Corallina officinalis. It is however extremely rare, being only found in England about Land's End. A more common and conspicuous, but equally handsome plant is Ptilota plumosa (Fig. 9), which is mostly confined to our northern coasts; although P. sericea, a smaller species, or variety, is common in the south, and easily distinguished from its congener, which it otherwise greatly resembles, by its jointed branchlets and pinnules. Callithamnion, Halurus and Griffithsia, articulate like Ceramium, furnish also several handsome species. (Fig. 5.)

The group Spyridiaceae contains only one English plant, Spyridia filamentosa, which is curiously and irregularly branched, the branches being articulate and of a pinky red. One of its kinds of fruit, consisting of crimson spores, is contained in a transparent network basket, formed by the favellae, or short branches, whence its name.

The Cryptonemiaceae are very numerous in genera and species. They all have inarticulate branches, some are thread-like. Grateloupia filicina is a neat little plant, met with rarely on the south and west coasts. Gigartina mamillosa, a common plant everywhere, is the plant sold, along with Chondrus crispus, as Irish or Carrageen moss. A handsome little plant, Stenogramme interrupta, is very rare, but it has been gathered both on the Irish and English coasts. The Phyllophorae, one species of which is frequent on all our shores, may be recognised by the way in which the points and surfaces of their fronds throw out proliferous leaves. Gymnogongrus has two British species, one much resembling Chondrus crispus, already named, of which it was formerly considered a congener. Their fructification is however very different. Ahnfeltia plicata is a curiouswiry, entangled plant, almost black in colour, and like horse-hair when dry, and can scarcely be mistaken. Cystoclonium purpurascens is very commonly cast up by the tide on most of our coasts. It varies in colour, but is easily distinguished by the spore-bearing tubercles imbedded in its slender branches. Callophyllis laciniata is a handsome species, of a rich crimson colour, and sometimes a foot square. It can scarcely have escaped the notice of the sea-side visitor, for it is widely distributed and often thrown out in great abundance; one writer describes the shore near Tynemouth as having been red for upwards of a mile with this superb sea-weed. Kalymenia reniformis is another of the broad, flat Algae, but it is scarcer, and of a colour not so conspicuous. Among the most frequent of our sea-weeds, both as growing in the rock pools and cast ashore, is Chondrus crispus, already twice referred to in connexion with its officinal uses. It is very variable in form, one author figuring as many as thirty-six different varieties. (Fig. 6.) Chylocladia clavellosa, which is sometimes cast ashore a foot and a half long, is closely set with branches, and these again clothed with branchlets in one or two series. The whole plant is fleshy, of a rose-red or brilliant pink colour, turning to golden yellow in decay. There is another small species, confined to the extreme north of Britain. Halymenia ligulata is another flat red weed, but sometimes very narrow in its ramifications. Furcellaria fastigiata has a round, branched, taper stem, swollen at the summit, which contains the fruit, consisting of masses of tetraspores in a pod-like receptacle. Schizymenia edulis, better known perhaps by its old name Iridea, is a flat, inversely egg-shaped leaf with scarcely any stem. It is one of the edible Algae, and pretty frequent in shady rock pools. Gloiosiphonia capillaris is a remarkably beautiful plant, and not common, being confined to certain parts of the southern coasts. The stem is very soft and gelatinous; the spores are produced in red globular masses imbedded in the marginal filaments, which have a fine appearance under the microscope when fresh.

The Rhodomeniaceae are purplish or blood-red sea-weeds, inarticulate, membranaceous, and cellular. Among the dark-coloured is Rhodomenia palmata, better known as dulse, a common and edible species. (Fig. 7.) Wormskioldia sanguinea is not only the most beautiful sea-weed, but the finest of all leaves or fronds. It is usually about six inches long, but sometimes nearly double that length and six inches broad, with a distinct midrib and branching veins, and a delicate wavy lamina, pink or deep red. The fruit is produced in winter from small leaflets growing upon the bare midrib. (Fig. 8.) The commonest of all red sea-weeds on our coast, one of the most elegant, and much sought after by sea-weed picture makers, Plocamium coccineum, belongs to this group. Calliblepharis ciliata and jubata are coarser plants, the latter being the more frequent. They were formerly included in the genus Rhodymenia, from which they were removed when their fruit was better understood.

Wrangelia and Naccaria are the only British genera in Wrangeliaceae. There is only one native species in each, both being rare, the latter especially.

The Helminthocladiae are also a limited group, of a gelatinous structure; so much so that on being gathered they feel like a bunch of slimy worms, whence the name of the family. Helminthora purpurea and divaricata with Nemaleon multifidum and Scinaia furcellata represent them in Britain. They are nearly all very rare, pretty plants, and very effective as microscopic objects.

The Squamariae, formerly included in the Corallinaceae, are a small group of inconspicuous plants resembling lichens, of a leathery texture, and growing on rocks and shells attached by their lower surface.

A single genus only, Polyides, represents the Spongiocarpeae. Polyides rotundus resembles Furcellaria fastigiata very closely, but differs widely in the fruit, which consists of spongy warts surrounding the frond, composed of spores and articulated threads.

Of the next group represented in Britain, Gelidiaceae, we have only one plant, Gelidium corneum, very common on our shores, and perhaps the most variable of all vegetable species.

The Sphaerococcidae include both membranaceous and cartilaginous species. Of the latter is Sphaerococcus coronopifolius, which cannot easily be mistaken, owing to the numerous berry-like fruits that tip its branchlets. It is rather rare on the northern, but often thrown ashore in large quantities on the southern coasts. The genus Delesseria has four British species, the largest being the well-known D. sinuosa, the fronds of which resemble an oak leaf in outline. The handsomest are D. ruscifolia and D. hypoglossum, which are more delicate and of a finer colour than sinuosa. There are three British species of Gracillaria, in two of which the branches are cylindrical, and in the other flat. G. compressa makes an excellent preserve and pickle, but unfortunately it is the rarest of the three. Nitophyllum is one of the greatest ornaments of this tribe. There are six British species, which are amongst the most delicate and beautiful of our native Algae.

The Corallinaceae are remarkable for the property they possess of absorbing carbonate of lime into their tissues, so that they appear as a succession of chalky articulations or incrustations. The most common is Corallina officinalis. There are two British species of Corallina, and two also of the nearly allied genus, Jania. Of the foliaceous group there are likewise two British genera, Melobesia and Hildenbrantia.

The next group, the Laurenciaceae, are cartilaginous and cylindrical or compressed, the frond in the greater portion of them being inarticulate and solid. They contain several species valued by collectors, although some of them are amongst our commonest plants. Their colour is, when perfect, a dull purple or brownish red, but they change under the influence of light and air, while fresh water is rapidly destructive to their tints. (Fig. 10.)

The Chylocladiae are curiously jointed plants, removed by Agardh to a new genus, Lomentaria, and a new order Chondriae. Bonnemaisonia asparagoides is the most rare and beautiful of the tribe.

The last tribe of red weeds, Rhodomelaceae, varies greatly in the structure of the frond, but the fruit is more uniform. Polysiphonia and Dasya contain the finest of the filiform division; the leafy one, Odonthalia, a northern form, is a very beautiful sea-weed both as respects form and colour. Well-grown specimens are not unlike a hawthorn twig, and of a blood red colour.

The plants of the sub-order Melanospermeae, are, like the red sea-weeds, exclusively marine. They are usually large and coarse, and confined mostly to comparatively shallow water. In the Laminariaceae we find the gigantic oarweeds already briefly referred to. Lessonia, which encircles in submarine forests the antarctic coasts, is an erect, tree-like plant, with a trunk from five to ten feet high, forked branches, and drooping leaves, one to three feet in length, and has been compared to a weeping willow. Sir Joseph Hooker says, that from a boat there may on a calm day be witnessed in the antarctic regions, over these submarine groves, "as busy a scene as is presented by the coral reefs of the tropics. The leaves of the Lessoniae are crowded with Sertulariae and Mollusca, or encircled with Flustra; on the trunks parasitic Algae abound, together with chitons, limpets, and other shells; at the base and among the tangled roots swarm thousands of Crustaceae and Radiata, while fish of several species dart among the leaves and branches." Of these and other gigantic melanosperms, flung ashore by the waves, a belt of decaying vegetable matter is formed, miles in extent, some yards broad, and three feet in depth; and Sir J. Hooker adds that the trunks of Lessonia so much resemble driftwood that no persuasion could prevent an ignorant shipmaster from employing his crew, during two bitterly cold days, in collecting this incombustible material for fuel. Macrocystis and Nereocystis are also giant members of this sub-order. Some of the Laminariae which form a belt around our own coasts not seldom attain a length of from eight to twelve feet. The common bladder-wrack (Fucus vesiculosus) sometimes grows in Jutland to a height of ten feet, and in clusters several feet in diameter. The colour of most of the plants in this sub-order is some shade of olive, but several of them turn to green in drying.

The first group, Ectocarpeae, is composed of thread-like jointed plants, the fructification of which consists of external spores, sometimes formed by the swelling of a branchlet. The typical genus, Ectocarpus, abounds in species, a dozen or so of which, very nearly allied plants, being found around our own shores. One or two of them are very handsome. There are also some very beautiful plants in the genus Sphacelaria, belonging to this group, several of them resembling miniature ferns. All the Sphacelariae are easily recognized by the withered appearance of the tips of the fruiting branches. Myriotrichia is a genus of small parasitical plants, the two British species of which grow chiefly on the sea thongs (Chorda).

The Chordariae are sometimes gelatinous in structure, in other cases cartilaginous. The fruit is contained in the substance of the frond. The genus Chordaria consists of plants which have the appearance of dark coloured twine. There are two British species, one being rather common. Chorda filum, sea-rope, another string-like sea-weed, grows in tufts from a few inches to many feet in length, and tapering at the roots to about the thickness of a pig's bristle. In quiet land-locked bays with a sandy or muddy bottom, it sometimes extends to forty feet in length, forming extensive meadows, obstructing the passage of boats, and endangering the lives of swimmers entangled in its slimy cords, whence probably its other name of "dead men's lines."

The Mesogloieae in a fresh state resemble bundles of green, slimy worms. There are three British species, two of which are not uncommon. Although so unattractive in external aspect, they, like many others of the same description, prove very interesting under the microscope. One of the cartilaginous species, Leathsia tuberiformis, has the appearance, when growing, of a mass of distorted tubers.

The species of Elachista, composed of minute parasites, are, as well as unattractive like the Mesogloieae, inconspicuous, but are beautiful objects when placed under the microscope. Myrionemae are also parasitic, and even smaller than the plants of the preceding genus.

In the Dictyoteae the frond is mostly flat, with a reticulated surface, which is sprinkled when in fruit with groups of naked spores or spore cysts. This tribe includes not a few of the most elegant among the Algae. In structure they are coriaceous, and include plants both with broad and narrow, branched and unbranched fronds. In Haliseris there is a distinct midrib. The largest of the British Dictyoteae is Cutleria multifida, sometimes found a foot and a half long; and the best known is doubtless Padina pavonia, much sought after by seaside visitors where it grows. Its segments are fan-shaped, variegated with lighter curved lines, and fringed with golden tinted filaments. (Fig. 11.) Owing to its power of decomposing light, its fronds, when growing under water, suggest the train of the peacock, whence its specific name. Taonia atomaria somewhat resembles Cutleria, but exhibits also the wavy lines of Padina. The plant of this group most often cast ashore is Dictyota dichotoma. It makes a handsome specimen when well dried, and is interesting on account of the manner in which it varies in the breadth of its divisions. The variety intricata is curiously curled and entangled. Dictyosiphon foeniculaceus, the solitary British example of its genus, is a bushy filiform plant, remarkable for the beautiful net-like markings of its surface. The Punctariae have flattened fronds, marked with dots, which sufficiently distinguish them from all the others. A small form is often found parasitic on Chorda filum, spreading out horizontally like the hairs of a bottle brush. Asperococcus derives its name from its roughened surface, occasioned by the thickly scattered spots of fructification.

The Laminariaceae are inarticulate, mostly flat, often strap-shaped. Their spores occur in superficial patches, or covering the whole frond. The plants of this order, as we have already seen, include the giants of submarine vegetation. In point of mass they constitute the larger part of our native Algae, although they number only a few species. They are popularly known as tangle or oarweeds, and the stems of Laminaria saccharina and the midrib of Alaria esculenta are used as food.

The Sporochnaceae are a small but beautiful tribe, inarticulate, and producing their spores in jointed filaments or knob-like masses, and remarkable for their property of turning from olive brown to a verdigris green when exposed to the atmosphere.

They are deep sea plants, or at least grow about low water mark. The largest of the group is Desmarestia ligulata, which, with the other British species, D. aculeata, is often cast ashore. The latter species, at an early period of its existence, is clothed with tufts of slender hairs, springing from the margin of the frond. Desmarestia viridis is the most delicate and also the rarest of the three. Nothing like fruit has been discovered on any of them. Arthocladia villosa and Sporochnus pedunculatus are branched sea-weeds, covered also with tufts of closely set hairs. Carpomitra Cabrerae, a rare species, bears, in common with the two preceding species, its spores in a special receptacle. In the first the receptacle is pod-like; in the second knotted; and in the last mitriform.

The concluding group of Algae is the Fucaceae, including the universally known sea wrack (Fucus). The frond in all of them is jointless. They are reproduced by means of antheridia and oogonia developed in conceptacles, clustered together at the apex of the branches. Both from their bulk and their decided sexual distinctions, they deserve to rank at the head of the order. Of all sea-weeds they are also perhaps of the greatest use to man. One of the most interesting among them is the Gulfweed (Sargassum bacciferum), occupying a tract of the Atlantic extending over many degrees of latitude. Pieces of it, and of its congener, S. vulgare, are occasionally drifted to our shores, and they consequently find a place in works on British Algae, although they have no claim to be considered native plants. On rocky coasts the various species of Fucus occupy the greater part of the space between tide-marks, the most plentiful being Fucus vesiculosus. F. serratus (Fig. 12) is the handsomest of the genus, the other species being F. nodosus, said to be the most useful for making kelp, and F. canaliculatus. Halidrys siliquosa is remarkable for its spore receptacles, which have quite the appearance of the seed vessel of a flowering plant. The species of Cystoseira, chiefly confined to the southern coasts, are also very interesting. Their submerged fronds are beautifully iridescent, and the stems, of the largest species at least, are generally covered with a great variety of parasites, animal and vegetable, the former consisting of Hydrozoa and Polyzoa, and other curious forms. Himanthalia lorea is another remarkable plant. It has conspicuous forked fruit-bearing receptacles; but the real plants are the small cones at the base of these, and from which they are shed when ripe.

As to conditions of site and geographical distribution, Algae do not differ from land plants. Latitude, depth of water, and currents influence them in the same way as latitude, elevation, and station operate on the latter; and the analogy is maintained in the almost cosmopolitan range of some, and the restricted habitat of others. Not many extra-European species of Desmids are known, but those of Diatoms are far more widely diffused, and extend beyond the limits of all other vegetation, existing wherever there is water sufficient to allow of their production; and they are found not only in water, but also on the moist surface of the ground and on other plants, in hot springs and amid polar ice. They are said to occur in such countless myriads in the South Polar Sea as to stain the berg and pack ice wherever these are washed by the surge. A deposit of mud, chiefly consisting of the shells of Diatoms, 400 miles long, 120 miles broad, and of unknown thickness, was found at a depth of between 200 and 400 feet on the flanks of Victoria Land in 70 deg. south latitude. Such is their abundance in some rivers and estuaries that Professor Ehrenberg goes the length of affirming that they have exercised an important influence in blocking up harbours and diminishing the depth of channels. The trade and other winds distribute large quantities over the earth, which may account for the universality of their specific distribution; for Sir Joseph Hooker found the Himalayan species to closely resemble our own. Common British species also occur in Ceylon, Italy, Virginia, and Peru. The typical species of the Confervaceae are also distributed over the whole surface of the globe. They inhabit both fresh and salt water, and are found alike in the polar seas and in the boiling springs of Iceland, in mineral waters and in chemical solutions. Some of the tropical ones are exceedingly large and dense. Batrachospermum vagum, in the next tribe, a native of England, is also found in New Zealand. An edible species of Nostochineae, produced on the boggy slopes bordering the Arctic Ocean, is blown about by the winds sometimes ten miles from land, where it is found lying in small depressions in the snow upon the ice. The common Nostoc of moist ground in England occurs also in Kerguelen's Land, high in the southern hemisphere. Floating masses of Monormia are often the cause of the green hue assumed by the water of ponds and lakes. Certain species of Oscillatoria of a deep red colour live in hot springs in India, and the Red Sea is supposed to have derived its name from a species of this tribe, which covers it with a scum for many miles, according to the direction of the wind. The lake of Glaslough in County Monaghan, Ireland, owes its colour and its name to Oscillatoria aerugescens, and large masses of water in Scotland and Switzerland are tinted green or purple by a similar agency. A few species of Siphoneae have a very wide range, two British species of Codium occurring in New Zealand. The Ulvaceae abound principally in the colder latitudes. Enteromorpha intestinalis, a common British species, is as frequent in Japan, where it is used, when dried, in soup. The Rhodosperms are found in every sea, although the geographical boundaries of genera are often well-marked. Gloiosiphonia, one of our rarest and most beautiful Algae, is widely diffused. Of Melanosperms the Laminariae affect the higher northern latitudes, Sargassa abound in the warmer seas, while Durvillaea, Lessonia, and Macrocystis characterize the marine flora of the Southern Ocean. The Fucaceae are most abundant towards the poles, where they attain their greatest size. The marine meadows of Sargassum, conceived by some naturalists to mark the site of the lost Atlantis, and which give its name to the Sargasso Sea, extending between 20 deg. and 25 deg. north latitude, in 40 deg. west longitude, occupy now the same position as when the early navigators, with considerable trepidation, forced through their masses on the way to the New World. Sargassum is drifted into this tract of ocean by currents, the plants being all detached; and they do not produce fruit in that state, being propagated by buds, which originate new branches and leaves. (Fig. 13.)

Owing to their soft, cellular structure, Algae are not likely to be preserved in a fossil state; but what have been considered such have been found as low down as the Silurian formation, although their identity has been disputed, and several of them, it is more than probable, belong to other orders, and some even to the animal kingdom. Freshwater forms, all of existing genera and species, are believed to have been detected in the carboniferous rocks of Britain and France; others also of the green-coloured division are said to occur from the Silurian to the Eocene, and the Florideae to be represented from the Lias to the Miocene. The indestructible nature of the shells of the Diatomaceae has enabled them to survive where the less protected species may have perished. Tripoli stone, a Tertiary rock, is entirely composed of the remains of microscopic plants of this tribe. It is from their silicious shells that mineral acquires its use in the arts, as powder for polishing stones and metals. Ehrenberg estimates that in every cubic inch of the tripoli of Bilin, in Bohemia, there are 41,000,000 of Gaillonella distans. Districts recovered from the sea frequently contain myriads of Diatoms, forming strata of considerable thickness; and similar deposits occur in the ancient sites of lakes in this and other countries.

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Before setting out in search of Algae the collector ought to provide himself with a pair of stout boots to guard his feet from the sharp-pointed rocks, as well as a staff or pole to balance himself in rock-climbing, which ought to have a hook for drawing floating weed ashore. A stout table-knife tied to the other end will be found very useful. A basket--a fishing-basket does very well--or a waterproof bag, for stowing away his plants, is also necessary. It is advisable to carry a few bottles for the very small and delicate plants, and care should be taken to keep apart, and in sea-water, any specimens of the Sporochnaceae; for they are not only apt to decay themselves but to become a cause of corruption in the other weeds with which they come in contact. These bottles should always be carried in the bag or pocket, never in the hand.