But having thus arranged, though the arrangement is but temporary, the specimens gathered, on slips of white paper, the next and most important point is their due examination and determination. This, in the present advanced state of Lichenology, is unquestionably, in many cases, a task of considerable difficulty, and in the short space at our disposal it would be quite impossible to give anything like an adequate explanation of the mode in which this is to be effected. Suffice it at present to say that sections must be made of the thallus to ascertain the character of its different layers, as also sections of the apothecia and spermagones to ascertain the nature of the spores and spermatia. For both purposes a good microscope, with 1/4-inch object-glass, is absolutely indispensable to the student. The examination of the spores, upon which, in so many cases, the determination of the species chiefly depends, should present little or no difficulty, at least to the fungologist. It may be readily effected by moistening the apothecium with water, and then, with a dissecting-knife, making a thin vertical section through its centre. Putting this on a glass slide, or in a compressorium, in a drop of hydrate of potash, and then placing it under the microscope, a view will be obtained of the asci, spores, paraphyses, hypothecium, &c., each of which may afterwards be insulated and examined more minutely in detail. Take, for example, the well-known beautiful yellow lichen (Physcia parietina), so common everywhere on walls, rocks, and trees, and treat a very thin section of the mature apothecium as before mentioned. Under the microscope it will appear as represented in Fig. 43.
In the same way the spermagones may be examined, when the nature of the sterigmata and spermatia will be apparent. By cutting across the thallus of the above species, we can perceive even by the naked eye that it consists of three different layers, which when microscopically examined present the appearance shown in the above figure.
But in addition to this microscopical examination, it is also requisite to observe the different chemical reactions produced on the asci or the hymeneal gelatine with iodine (I), which will tinge these either bluish or reddish wine-coloured, or else leave them uncoloured. Similarly the thallus, including both the cortical layer and the medulla, may be tested with hydrate of potash (K), and hypochlorite of lime (C), the latter being applied either by itself or added to K when wet. In some cases no reaction will be produced by these either upon the cortical stratum or the medulla; in others they will be tinged yellowish or reddish. The formulæ for the preparation of these reagents are: for iodine, iodine, gr. j; iodide of potash, gr. iij, distilled water, 1/2 oz.; for hydrate of potash, equal weights of caustic potash and water; for hydrochlorite of lime, chloride of lime and water of any strength. After correctly ascertaining the specific name of the specimens collected, this is to be written on the slips of paper to which they are affixed, above the locality and date, and the best of them, including all varieties and forms, selected for subsequent mounting in the herbarium. This may be effected either in the same way as the mounting of phanerogamic plants, or by affixing the specimens to pieces of millboard covered with white paper, and arranging them according to the order of the genera and species in the system of classification which may be adopted. For facility of reference the latter is undoubtedly the preferable method; and if the cards are disposed in a cabinet with shallow drawers, they will not, so far at least as our British species are concerned, be found to occupy too much space.
XIV.
SEAWEEDS.
By W. H. Grattann.
In some articles published in 'Science-Gossip' a few years ago, I gave some directions for collecting and preserving Marine Algæ, or seaweeds, and although, I think, it will be difficult to simplify those directions, or even to add much that would be really serviceable to young beginners in this delightful pursuit, it is my intention, in going over the ground once more, to be as explicit as I possibly can; and here, on the threshold of the subject, I have a few words to say to one or two occasional contributors to that journal, who, in calling attention to the beauty of marine vegetation, and urging young persons to collect and preserve Algæ, have advised them to ignore books on the subject, and go to the shore, use their own eyes, and collect for themselves, &c. I am sorry very greatly to differ from such advice. Collecting in this way may be amusing enough to those who care not for science, but when it leads to parcels of seaweeds, picked up at random, being sent to botanists with a request that the names of such plants should be sent to the writer, it is the reverse of pleasure to the scientific botanist, for it gives him infinite trouble, and enables him to convey but very imperfect information to his applicant. The editor of that journal has often been thus appealed to, and packages of decayed rubbish have frequently been sent to me for examination, containing species or rather fragments of plants, which, for the most part, were utterly worthless and defied identification.
Almost all collectors commence by mounting plants which a little experience proves to be really what the old poet termed "alga projecta vilior"; but as seaweed-gathering, like everything else, requires practice, beginners must not be disappointed because they do not find rarities or fine specimens whenever and wherever they may seek for them.
When I think of the difficulties I experienced at the outset of my study of marine botany, especially in the collecting and drying of seaweeds, I feel strongly inclined to urge all beginners to obtain some information concerning Marine Algæ before they go to the shore to collect for themselves. A very few hours of study with an experienced algologist, or even a perusal of some illustrated work on British algæ, will save much trouble and materially assist the unpractised eye in selecting specimens for the herbarium. I may here mention as highly useful to incipient algologists Dr. Landsborough's 'British Seaweeds' and Professor Harvey's 'Manual,' either of which may be obtained for a few shillings; but if my readers are resident in London, I advise them to pay a few visits to the Library of the British Museum, and there inspect Dr. Harvey's 'Phycologia Britannica.' In this magnificent work they will find coloured figures of nearly every British seaweed, with drawings from magnified portions, and various structural details of the highest value to students; and I once more impress on all collectors the importance of some degree of book-learning ere they sally forth, bag or vasculum in hand, to cull the lovely "flowers of the ocean," or gather what best may please them from the rejectamenta on the shore.
If the collector wishes to learn, not merely the names of plants, but to distinguish species, he will do well to provide himself with a copy of Harvey's little volume the 'Synopsis of British Seaweeds,' and a Stanhope or Coddington lens, by means of which he can examine portions of delicate plants as he finds them, and compare them with the descriptions given in the 'Synopsis'; in this way, if he have any success during his excursions, he will quickly become familiar with most of the plants which are cast ashore or grow within tide-marks.
Time will not admit of, neither is space at present available for, a single line beyond what may be practically serviceable to my youthful readers; therefore I will hasten to describe the course of action in seaweed-collecting as I have practised it for many years. At once, then, to the shore, but not to the sandy shore, for only useless decayed rubbish, or here and there some straggling plants of Zostera marina, or grass-wrack, will be met with there. The collector must away to the rocks, and search carefully every pool he meets with, from a little distance below high-water mark, and so on down to the water's edge, always remembering that it is better to collect while the tide is receding than as it is coming in.
Presuming that few persons will think of collecting seaweeds much earlier than the month of May, let me observe that most of the accessible species of olive and green plants which grow on rocky shores and in tide-pools, will be found from May to June in pretty fair condition, but very few red plants, except those which grow on the shady sides of rock-pools, or under the shelter of the larger olive weeds, will be met with until a considerable space is laid bare by the receding water at the low spring tides, about a day or two before and after the full moon.
As nearly all the rare red weeds grow in deep water, they are seldom taken in any degree of perfection unless they are dredged; but in the summer months, say from June to the end of August, many fine plants are occasionally thrown up from deep water, and others are found growing on the stems of the great oar-weeds, portions of which are cast ashore, beautifully fringed with one or more species of Delesseria and other rare Rhodosperms—in fact, during the rising tide, diligent collectors may secure many a lovely deep-water plant as it comes floating in, but which, if allowed to remain long exposed to the action of sunlight, will fade in colour and decompose before it can be mounted. This is especially the case with all the soft gelatinous red plants, such as the Callithamnia, and all the Gloiocladiæ, as well as a few of the softer olive weeds; and here I may observe that there is one genus of beautiful olive plants, the Sporochnaceæ, which must on no account be put into the vasculum with any of the delicate red plants, for they not only very rapidly decompose, but injure almost all others with which they are placed in contact. The species are not numerous, and they may be easily recognized, after having been previously studied from the coloured figures either in Harvey's 'Phycologia,' or in Bradbury and Evans's 'Nature-printed Seaweeds.' It is also a curious fact respecting this genus, that while they are all of a beautiful olive tint in the growing state, they invariably change to a fine verdigris-green in drying; and indeed this is very generally the case with the filamentous olive weeds, the Fuci, or common rock-weeds, as constantly turning quite black after mounting: whence the term, that of "Melanosperm," which is given to the subdivision to which all the olive weeds belong.
As there are so few seaweeds which have generally known common names, I shall make no apology for using the names by which they are known to science, presuming that all intending collectors will, as I have already suggested, gain some knowledge of Terminology ere they go out "seaweeding."
Beginners should be cautioned against the very natural error of bringing home too many plants at a time; they must be moderate in their gatherings, or be content to risk the loss of some choice specimens, which will decompose unless they are attended to before night. The first thing to be done upon arriving at home, is to empty the collecting-bag into a white basin of sea-water, and to select the best and cleanest plants as soon as possible, giving each a good swill before placing it in another vessel of clean water, and getting rid of rejected plants at once, so that the basin first used will be available for rewashing the weeds before they are severally placed in the mounting dish. When a day is fixed on for seaweeding, the collector should order a large bucket of clean sea-water, which, after being left to settle, should be strained through a towel, so as to be as free as possible from sand and dirt. Two or three large pie-dishes will be necessary, the deeper the better, and white, if such can be obtained. Place these on a separate table with towels under them, and reserve a table specially for the mounting dish and the parcels of papers, calicoes, and blotting-papers. The large white bath used in photography is very well adapted for mounting seaweeds; the lip at one corner is convenient for pouring off soiled water, and its form—that of an oblong—is most suitable for receiving the papers on which the plants are to be mounted. Beside this vessel should be placed the following implements—a porcupine quill, two camel-hair pencils (one small, the other large and flat), a pair of strong brass forceps, a penknife, a pair of scissors, a small sponge, an ivory paper-knife, and two thin plates of perforated zinc somewhat less in length and breadth than the inside of the mounting dish.
Smooth drawing paper, or fine white cartridge paper, is generally employed for mounting. The operator should be provided with three different sizes of paper, and these should have each a piece of very fine calico and four pieces of blotting-paper to correspond. The process of mounting one of the filamentous or branching species is as follows:—The specimen being cleaned and placed in the mounting dish, a piece of paper of suitable size is laid on one of the perforated zinc plates, and both are then slipped quickly under the floating weed. The root or base of the specimen is then pressed down on the paper with a finger of the left hand, while the right hand is employing the forceps or porcupine quill in arranging the plant in as natural a position as possible, ere the zinc plate is gently and gradually raised at the top or bottom, as may be necessary, to ensure a perfect display of every portion of the plant; but if, upon drawing it out of the water, it should present an unsightly appearance from too thick an overlapping of the branches, the whole must be reimmersed, and a little pruning of superfluous portions may be employed with advantage to the specimen and satisfaction to the operator. Care should be taken that the water be drained off the paper as completely as possible before the calico is laid over the plant, and this is accomplished by raising the paper containing the plant as it still lies on the zinc plate, and transferring it to a thin board placed in an inclined position against one of the basins, and with the large camel-hair pencil paint off the water as it runs away from the specimen, and absorb what remains, when the paper is laid flat, with the sponge. Delicate species may be left to drain for a few minutes, while the operator is arranging other specimens. When the water is sufficiently drained off, the paper is then laid on the blotter, and the piece of calico is placed upon the plant—a sheet of blotter being laid upon the calico.
Care should be observed in subjecting plants to pressure, which, in the first instance, should be sufficient only to help the absorption of water. The first set of blotting-papers should be changed in half an hour after the whole batch of specimens have been placed in the press, and these must be thoroughly dried before they are used again. After the second or third change of blotters, the plants should remain under strong pressure for two or three days; but the pieces of calico must not be removed until it is pretty certain that the papers and plants are quite dry.
With the exception of the Fuci or common rock-weeds, I never place seaweeds in fresh water: with these, especially Fucus serratus, F. nodosus, F. vesiculosus, and F. canaliculatus, a few hours' immersion in fresh water is an advantage, as it soaks the salt out of their fronds and renders them more pliable. As all the Fuci turn black in drying, and few of them adhere well to paper, I arrange my specimens in single layers between the folds of a clean dry towel, and keep them under pressure until they are quite dry; they may then be put away loosely, or gummed on sheets of paper.
The foregoing directions for mounting filamentous seaweeds are applicable to all the branching species of Olive, Red, and Green plants; but in each of the three subdivisions there are a few species which are so gelatinous—in fact, so soft and spongy, that they require the utmost care during pressure, otherwise they adhere to the calico and break off in fragments as it is drawn away. Such plants must be left to dry in a horizontal position for an hour or so before the calico and blotters are placed over them, and pressure must be very slight until they have adhered closely to the paper. Among the Chlorosperms, or green plants, there are the various species of Codium, young plants of which only are manageable or indeed desirable. In the Melanosperms, some species of the genus Mesogloia will require care and patience in mounting, as well as the long string-like plant, known as Chorda filum; and again, the spreading tuberous mass called Leathsia tuberiformis, portions of which should be cut from the rock, the sand scraped and washed out, then laid on the wet paper, and allowed to shrink for some hours ere calico blotters and pressure be applied. These difficulties are much more numerous among the Rhodosperms, or red seaweeds, experience only teaching the best method of treatment. I will, however, mention the names of some very troublesome plants, the fronds of which, if subjected to pressure too soon, burst and discharge their carmine contents; not only presenting an unsightly appearance, but destroying the specimen. These are Griffithsia corallina, Dudresnaia coccinea, Naccaria Wigghii, all the Chylocladia, and the rare Gloiosiphonia, as well as the slimy worm-like plant known as Nemalion multifidum.
In addition to these troubles among the red plants, there is an opposite difficulty connected with several Rhodosperms which must be pointed out; and that is owing to an absence or scarcity of gelatine in their substance, which is in some of a stout, leathery, or horny nature, and in others is due to a coating of carbonate of lime, which completely envelops the vegetable structure. Among the former may be mentioned the several species of Phyllophora, and several among the genera Gigartina, Chondrus, and Sphærococcus; and in the latter, all the calcareous Algæ, especially the well-known Corallina officinalis and Jania rubens. All these, and several others of a membraneous nature, among the olive as well as the red weeds, must be first mounted in the ordinary manner, and when they are tolerably dry and begin to shrink away from the paper, fill the mounting-dish with stale skimmed milk; refloat the plants on their papers in the milk, and indeed go through the same process as before with the sea-water, but be careful to absorb all the milk from off the surface of the plants and the back of the papers, and then, after the usual time for drying and pressing, the most obstinate seaweed will be found adhering perfectly to the paper, and will remain so permanently.
One more difficulty must be referred to for the benefit of young beginners, who, in mounting some of the Laminaria and that peculiar olive weed called Himanthalia lorea, may wish to preserve the thick-branching roots and stems. First wash the roots as clean as possible, and then, with a sharp penknife, make a clean cutting horizontally of the whole root and some little distance up the thick round stem; then, after having removed the cut portions, place the inner surface of the root and stem on the paper, and the gelatinous matter which oozes from the plant will cause the roots to adhere firmly to the paper, and in drying, the usual olive tint of the various species of Laminaria will be finely preserved. Some botanists employ a mixture made of isinglass, dissolved in alcohol, to fix some of the horny or robust species on paper; but if gum be made use of, it is better to employ gum tragacanth than gum-arabic, because, in drying, the former has none of that objectionable glare which is peculiar to gum arabic.
As regards the best method of pressing seaweeds, I think I can hardly do better than refer my readers to the figure of a Seaweed Press (Fig. 45), which I invented for myself many years ago, in which I have pressed many thousands of beautiful seaweeds. Almost any degree of pressure can be obtained in it: first, by the thumb-screws on the iron rods at each corner, and, finally, by means of the clamp which is strapped on the top of the press. Any intelligent cabinet-maker or ironmonger could provide such a press from an inspection of the figure; the cost, of course, varying with the dimensions and the number of boards.
With respect to localities favourable to seaweed-gathering, I may specially mention the south coast of Devon; from Exmouth, where Bryopsis and Padina pavonia grow in perfection, to Torquay and the coves of Torbay, and down the coast to Plymouth, Cawsand Bay, and finally Whitsand Bay, the "happy hunting-grounds" of the enthusiastic algologist. On the north-east coast, Filey and Whitby must be mentioned, as well as the shores upwards from Tynemouth to Whitley. Peterhead is also a good locality, the rare Ectocarpus Mertensii, Odonthalia dentata, and Callithamnion floccosum being found there in abundance. Other favourable stations in Scotland, well known to me, are Lamlash Bay and Whiting Bay; nor must the Isle of Wight be forgotten, for in the rock-pools, at Shanklin especially, the most magnificent form of Padina pavonia may be found growing during the summer months in the utmost profusion.
In conclusion, I beg leave to inform my readers that I have recently published a volume on British Marine Algæ, in which every species that is likely to be met with by ordinary collectors is described, and every British seaweed that is capable of illustration in a work intended for popular information, is figured from plants in my own possession, and, in addition, diagrams and figures from drawings of magnified portions, illustrative of structure and fructification, appear throughout the pages of my work.