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CHAPTER VI.

OF HERBARIA.

To a Botanist who studies the science with much attention, and with a view to becoming perfectly acquainted with it, neither books nor the most elaborate descriptions prove sufficient. He finds it indispensable to have continually within his reach some portion of as many species as he can procure. If he has admission to a botanical garden, a great many species may thus be readibly accessible; although, even in such a case, it is only at particular periods that he can study the flowers and fruits of any of them: a garden, too, seldom contains more than a fifteenth or a tenth of the number of known species; and far more frequently not a twentieth.

For these reasons, Botanists have contrived a method of preserving, by drying and pressure, specimens of plants which represent all that it is most essential to recognise. A collection of such specimens was formerly known by the expressive name of Hortus siccus; but is now universally called a Herbarium. If well prepared and arranged, such a collection is invaluable to any working Botanist, because it enables him instantly, at all times, to compare plants themselves with each other, and with the accounts of other Botanists; or to examine them with reference to points of structure not previously considered. It will, therefore, be useful to explain, shortly, the best modes of preparing, arranging, and preserving herbaria.

What is called the specimen of a plant is a small shoot bearing flowers and fruit, either together or separately, pressed flat and dried, so that it may be conveniently fixed upon a sheet of paper. As a plant is, in all cases, an aggregation of individuals growing upon exactly the same plan, and producing the same kind of reproductive organs, it follows that a single shoot, comprehending leaves, flowers, and fruit, is a representation of the largest tree of the forest, and will give as

distinct an idea of the individual as if a huge limb were before the Botanist. It is this fact that enables us to form herbaria. Besides the dried twigs thus described, a herbarium should contain specimens of the wood of each species, and also a collection of fruits and seeds, which, being often large, hard, and incapable of compression, are not fit to be incorporated with the dried specimens themselves.

In selecting specimens for drying, care must be taken that they exhibit the usual character of the species; no imperfect or monstrous shoot should be made use of. If the leaves of different parts of the species vary, as is often the case in herbaceous plants, examples of both should be preserved. The twig should not be more woody than is unavoidable, because of its not lying compactly in the herbarium. If the flowers grow from a very large woody part of the trunk, as is often the case in some Malpighias, Cynometra, &c., then they should be preserved with a piece of the bark only adhering to them. It is also very important that ripe fruit should accompany the specimen. When the fruit is small, or thin, or capable of compression without injury, a second dried specimen may be added to that exhibiting the flowers; but when it is large and woody, it must be preserved separately, in a manner I shall presently describe.

Next to a judicious selection of specimens, it is important to dry them in the best manner. For this purpose various methods have been proposed; some of the simplest and most practicable may be mentioned. If you are in a country where there is a great deal of sun-heat, it is an excellent plan to place your specimen between the leaves of a sheet of paper, and simply to pour as much sand or dried earth over it as will press every part flat, and then to leave it in the full sunshine. A few hours are often sufficient to dry a specimen thoroughly in this manner. But in travelling, when conveniences of this kind cannot be had, and in wild uninhabited regions, it is better to have two or more pasteboards of the size of the paper in which your specimens are dried, and some stout cord or leathern straps. Having gathered specimens until you are apprehensive of their shrivelling, fill each sheet of paper with as many as it will contain; and, having thus

formed a good stout bundle, place it between the pasteboards, and compress it with your cord or straps. In the evening, or at the first convenient opportunity, unstrap the package, take a fresh sheet of paper, and make it very dry and hot before a fire; into the sheet, so heated, transfer the specimens from the first sheet of paper in your package; then dry that sheet, and shift into it the specimens lying in the second sheet; and so go on, till all your specimens are shifted; then strap up the package anew, and repeat the operation at every convenient opportunity, till the plants are dry. They should then be transferred to fresh paper, tied up rather loosely, and laid by. Should the Botanist be stationary, or in any civilised country, he may dry his paper in the sun; or, if the number of specimens he has to prepare is inconsiderable, he may simply put them between cushions in a press resembling a napkin-press, laying it in the sun, or before a hot fire. It is extremely important that specimens should be dried quickly, otherwise they are apt to become mouldy and rotten, or black, and to fall in pieces. Notwithstanding all the precautions that can be taken, some plants, such as Orchidacea, will fall in pieces in drying: when this is the case, the fragments are to be carefully preserved, in order that they may be put together when the specimen is finally glued down. In many cases, particularly those of Coniferæ, Ericæ, &c., the leaves may be prevented falling off by plunging the specimen, when newly gathered, for a minute into boiling water. The great objects in drying a specimen are, to preserve its colour, if possible, which is not often the case, and not to press it so flat as to crush any of the parts, because that renders it impossible subsequently to analyse them.

Specimens of wood should be truncheons, five or six inches long, and three or four inches in diameter, if the plant grows so much. They should be planed smooth at each extremity, but neither varnished nor polished.

Specimens of fruits simply require to be dried in the sun. When specimens shall have been thoroughly dried, they should be fastened by strong glue, not gum nor paste. to half-sheets of good stout white paper: the place where they were found, or person from whom they were obtained, should

be written at the foot of each specimen, and the name at the lowest right-hand corner. If any of the flowers, or fruits, or seeds, are loose, they should be put into small paper cases, which may be glued, in some convenient place, to the paper. These cases are extremely useful; and fragments so preserved, being well adapted for subsequent analysis, will often prevent the specimen itself from being pulled in pieces.

The best size for the paper appears, by experience, to be 10 inches by 16. Linnæus used a size resembling our foolscap; but it is much too small; and a few employ paper 11 inches by 18; but that is larger than is necessary, and much too expensive.

In analysing dried specimens, the flowers or fruits should always be softened in boiling water: this renders all the parts pliable, and often restores them to their original position.

In arranging specimens, when thus prepared, every species of the same genus should be put into a wrapper formed of a whole sheet of paper, and marked at the lower left corner with the name of the genus. The genera should then be put together according to their natural orders.

In large collections it is often found difficult to preserve that exact order which is indispensable to the utility of a herbarium; and, accordingly, we constantly find Botanists embarrassed by multitudes of unarranged specimens. As this is a great evil, I trust that a few hints upon the subject may not be without their use; especially as, by attending to them myself, I have probably not 500 unarranged specimens in a herbarium of more than 30,000 species. Never suffer collections, however small, to accumulate; but, the very day, if possible, that a parcel of dried plants arrives, put each in its place. For this purpose they should not be glued down; but each species, with a ticket explaining its origin, name, &c., should be laid loose upon a half-sheet of waste paper, and then put into the cover of the genus to which it belongs: if the genus is not recognised, and there is no time for determining it, then take a cover marked with the name of the order at its lower left-hand corner, and put them in it; or, if the order is not known, then put the specimens into covers marked with the names of countries instead of orders,

after which you can examine them, from time to time, as opportunities may occur: in the herbarium above named, there are about 300 species thus laid by for consideration. Afterwards, when leisure permits, those generic covers in which there appears to be the greatest accumulation of loose specimens should be examined, the species compared and sorted, new species glued upon fresh half-sheets of paper, and duplicates taken out. The advantage of this plan is, that, under any circumstances, if it is wished to consult a particular order, all the materials you possess will be found, in some state or other, collected into one place. I am persuaded that, if this simple method were attended to, the confusion now so common in herbaria, and which renders so many of them almost useless, would never exist.

Fruits, if large, will be placed loose on shelves, in cases with glass fronts; or, if smaller, in little bottles, in which also seeds should be preserved; each fruit or bottle being labelled, and the whole arranged according to natural order. Specimens of wood may be conveniently combined with a carpological collection, and arranged on the same plan. When the sections of wood are very large, as is sometimes the case, there may be an extra compartment at the base of the case, in which they can be placed.

The cases in which the specimens are arranged may be made of any well-seasoned timber; mahogany is best; but pine wood will answer the purpose. They should consist of little closets, of a size convenient for moving from place to place; of which, two, placed one on the other, will form a tier. Each closet should have folding-doors, and its shelves should be in two rows: the distance from shelf to shelf should be six inches. The sides and ends of the closets should be made of 3-inch board; but for the shelves 3-inch is sufficient.

To preserve plants against the depredations of insects, by which, especially the little Anobium castaneum, they are apt to be much infested, it has been recommended to wash each specimen with a solution of corrosive sublimate in camphorated spirits of wine; but, independently of this being a doubtful mode of preservation, it is expensive, and, in large collec