Before setting out in search of Algæ 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 Sporochnaceæ; 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 Algæ 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 Algæ 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., 7½ in. by 5¼ in., and 10 in. by 7½ 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.
The very gelatinous plants require particular treatment. One way is to put them in drying paper and under a board but to apply no other pressure, change the drying paper at least twice during the first half hour, and after the second change of dryers apply very gentle pressure, increasing it until the specimens are fully dry. A safer and less troublesome way, for the efficacy of which we can vouch, is to lay down the plants and dry them without any pressure, afterwards damping the back of the mounting papers and placing them in the drying press. Some Algæ will scarcely adhere to paper. These should be pressed until tolerably dry, then be immersed in skim-milk for a quarter of an hour, and pressed and dried as before. A slight application of isinglass, dissolved in alcohol, to the under side of the specimen is sometimes necessary. Before mounting, or at all events before transference to the herbarium, care should be taken to write in pencil on the back of the paper the name of the plant, if known, the place where gathered, and the date. The coarse olive weeds, such as the bladder-wrack, Halidrys, and the like, may in the case of a short visit to the coast be allowed to dry in an airy place, and taken home in the rough. Before pressing, in any case, they should be steeped in boiling water for about half an hour to extract the salt, then washed in clean fresh water, dried between coarse towels, and pressed and dried in the same way as flowering plants. A collection of Algæ may be fastened on sheets of paper of the usual herbarium size and kept in a cabinet or portfolios, or attached to the leaves of an album. For scientific purposes, however, the latter is the least convenient way.
There are few objects more beautiful than many of the sea-weeds when well preserved; but the filiform species, especially those of the first sub-order, do not retain their distinguishing characters when pressed as has been described. Portions of these, however, as well as sections of stems and fruit, may be usefully dried on small squares of thin mica, for subsequent microscopic examination, or they may be mounted on the ordinary microscope slides. This is the only course possible with Desmids and Diatoms. The former are to be sought in shallow pools, especially in open boggy moors. The larger species commonly lie in a thin gelatinous stratum at the bottom of the pools, and by gently passing the fingers under them they will be caused to rise towards the surface, when they can be lifted with a scoop. Other species form a greenish or dirty cloud on the stems and leaves of other aquatic plants, and by stripping the plant between the fingers these also may be similarly detached and secured. If they are much diffused through the water, they may be separated by straining through linen; and this is a very common way of procuring them. Living Diatoms are found on aquatic plants, on rocks and stones, under water or on mud, presenting themselves as coloured fringes, cushion-like tufts, or filmy strata. In colour the masses vary from a yellowish brown to almost black. They are difficult, both when living and dead, to separate from foreign matter; but repeated washings are effectual in both cases, and, for the living ones, their tendency to move towards the light may also be taken advantage of. When only the shells are wanted for mounting, the cell contents are removed by means of hydrochloric and nitric acid. The most satisfactory medium for preserving fresh Desmids and Diatoms is distilled water, and if the water is saturated with camphor, or has dissolved in it a grain of alum and a grain of bay salt to an ounce of water, confervoid growths will be prevented. For larger preparations of Algæ, Thwaites' fluid is strongly recommended. This is made by adding to one part of rectified spirit as many drops of creasote as will saturate it, and then gradually mixing with it in a pestle and mortar some prepared chalk, with sixteen parts of water; an equal quantity of water saturated with camphor is then to be added, and the mixture, after standing for a few days, to be carefully filtered.
For authorities on the morphology and classification of the Algæ, students may be referred to Sachs' "Text Book" and Le Maout's "System of Botany," of which there are good translations, and the "Introduction to Cryptogamic Botany," by the Rev. M. J. Berkeley; for descriptions and the identification of species, to the text and figures of Harvey's "Phycologia Britannica," and "Nature-Printed Sea-weeds." Both of these are however costly. Among the cheaper works are "British Sea-weeds," by S. O. Gray (Lovell, Reeve & Co.), "Harvey's Manual" and an abridgment by Mrs. A. Gatty, with reduced but well executed copies of the figures, of the Phycologia. This synopsis can often be picked up cheap at second-hand bookstalls; and there is a very excellent low-priced work suitable for amateurs, Grattann's "British Marine Algæ," containing recognizable figures of nearly all our native species. Landsborough's "Popular History of British Sea-weeds," and Mrs. Lane Clarke's "Common Sea-weeds," are also cheap and useful manuals on the subject.
SHELLS.