Part 2

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.

Sea-weeds, as every visitor to the coast knows, are torn up in great numbers by the waves, especially during storms, and afterwards left on the shore by the retiring tide. Many shallow-growing species are also to be found attached to the rocks, and in the rock pools, between high and low water mark. There are three points on the beach where the greatest accumulations of floating Algae are found: high water mark, mid-tide level, and low water mark. Low water occurs about five or five and a half hours after high water. The best time for the collector to commence is half an hour or so before dead low water. He can then work to the lowest point safely, and, retiring before the approaching tide, examine the higher part of the beach up to high water mark. If the coarse weeds in the rock pools and chinks are turned back, many rare and delicate Algae will be found growing under them, especially at the lowest level. The most effective method of collecting the plants of deeper water is by dredging, or going round with a boat at the extreme ebb, and taking them from the rocks and from the Laminaria stems, on which a great number have their station. Stems of Laminaria thrown out by the waves should also be carefully examined. In all cases the weed should be well rinsed in a clear rock pool before being put away in the bag or other receptacle.

The next thing to be considered is the laying out and preserving of the specimens selected for the herbarium. Wherever possible these should be laid out on paper, and put under pressure as soon as gathered, or on the same day at all events. When this is impracticable, they may be spread between the folds of soft and thick towels and rolled up. Thus treated the most delicate plants will keep fresh until next day. Another way is to pack the plants in layers of salt, like herrings; but the most usual method of roughly preserving sea-weeds collected during an unprepared visit to the shore is by moderately drying them in an airy room out of the direct rays of the sun. They are then to be placed lightly in bags, and afterwards relaxed by immersion and prepared in the usual way. The finer plants, however, suffer more or less by this delay. If carried directly home from the sea the plants should be emptied into a vessel of sea-water. A flat dish, about fourteen inches square and three deep, is then to be filled with clean water. For most plants this may be fresh, for some it is essential that it should be salt. Some of the Polysiphonias and others begin to decompose at once if placed in fresh water. The Griffithsias burst and let out their colouring matter, and a good many change their colour. The appliances required are some fine white paper--good printing demy, thirty-six pounds or so in weight per ream, does very well,--an ample supply of smooth blotting paper, the coarse paper used by grocers and called "sugar royal," or, best of all, Bentall's botanical drying paper, pieces of well-washed book muslin, a camel's hair brush, a bodkin for assisting to spread out the plants, a pair of scissors, and a pair of forceps. The mounting paper may be cut in three sizes: 5 in. by 4 in., 71/2 in. by 51/4 in., and 10 in. by 71/2 in. Then having selected a specimen, place it in the flat dish referred to above, and prune it if necessary. Next take a piece of the mounting paper of suitable size, and slip it into the water underneath the plant, keeping hold of it with the thumb of the left hand. Having arranged the plant in a natural manner on the paper, brush it gently with the camel's hair brush to remove any dirt or fragments, draw out paper and plant gently and carefully in an oblique direction, and set them on end for a short time to drain. Having in this way transferred as many specimens as will cover a sheet of drying paper, lay them upon it neatly side by side, and cover them with a piece of old muslin. Four sheets of drying paper are then to be placed upon this, then another layer of plants and muslin and four more sheets of drying paper, until a heap, it may be six or eight inches thick, is built up. Place this between two flat boards, weighted with stones, bricks, or other weights; but the pressure should be moderate at first, otherwise the texture of the muslin may be stamped on both paper and plant. The papers must be changed in about three hours' time, and afterwards every twelve hours. In three or four days, according to the state of the weather, the muslin may be removed, the plants again transferred to dry paper, and subjected to rather severe pressure for several days.