Online Encyclopedia
Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.
HERBARIUM, or HORTUS
Online EncyclopediaEncyclopedia Home :: HEG-HIG
del.icio.us it!
|
See also:HERBARIUM, or HORTUS Siccus, a collection of See also:plants so dried and preserved as to illustrate as far as possible their characters. Since the same plant, owing to peculiarities of See also:climate, See also:soil and situation, degree of exposure to See also:light and other influences may vary greatly according to the locality in which it occurs, it is only by gathering together for comparison and study a large See also:series of examples of each See also:species that the See also:flora of different regions can be satisfactorily represented. Even in the best equipped botanical See also:garden it is impossible to have, at oiie and the same See also:time, more than a very small percentage of the representatives of the flora of any given region or of any large See also:group of plants. Hence a See also:good herbarium forms an indispensable See also:part of a botanical museum or institution. There are large herbaria at the See also:British Museum and at the Royal Gardens, See also:Kew, and smaller collections at the botanical institutions at the See also:principal British See also:universities. The See also:original herbarium of See also:Linnaeus is in the See also:possession of the Linnaean Society of See also:London. It was See also:purchased from the widow of Linnaeus by Dr (afterwards See also:Sir) J. E. See also: It is also rich in the types of Australian plants in the collections of Sir See also:Joseph See also:Banks and See also:Robert See also: The tough but flexible coarse See also:grey paper (See also:German Fliesspapier), upon which on the See also:Continent specimens are commonly fixed by gummed strips of the same, is less hygroscopic than See also:ordinary See also:cartridge paper, but has the disadvantage of affording harbourage in the inequalities of its See also:surface to a See also:minute See also:insect, See also:Atropos pulsatoria, which commits See also:great havoc in See also:damp specimens, and which, even if noticed, cannot be dislodged without difficulty. The majority of plant specimens are most suitably fastened on paper by a mixture of equal parts of See also:gum tragacanth and gum arabic made into a thick See also:paste with See also:water. Rigid leathery leaves are fixed by means of See also:glue, or, if they See also:present too smooth a surface, by stitching at their edges. Where, as in private herbaria, the specimens are not liable to be handled with great frequency, a stitch here and there See also:round the See also:stem, tied at the back of the See also:sheet, or slips of paper passed over the stem through two slits .in the sheet and attached with gum to its- back, or simply strips of gummed paper laid across the stem, may be resorted to. To preserve from See also:insects, the plants, after mounting, are often brushed over with a liquid formed by the See also:solution of a lb. each of corrosive sublimate and carbolic See also:acid in r See also:gallon of methylated See also:spirits. They are.then laid out to dry on shelves made of a network of stout galvanized See also:iron See also:wire. The use of corrosive sublimate is not, however, recommended, as it forms on drying a fine See also:powder which when the plants are handled will rub off and, being carried into the See also:air, may prove injurious to workers. If the plants are subjected to some See also:process, before mounting, by which injurious organisms are destroyed, such as exposure in a closed chamber to vapour of See also:carbon bisulphide for some See also:hours, the presence of pieces of camphor or See also:naphthalene in the See also:cabinet will be found a sufficient preservative. After mounting are written—usually in the right-See also:hand corner of the sheet, or on a See also:label there affixed—the designation of each species, the date and See also:place of gathering, and the name of the See also:collector. Other particulars as to See also:habit, See also:local abundance, soil and claim to be indigenous may be written on the back of the sheet or on a slip of See also:writing paper attached to its edge. It is convenient to place in a small envelope gummed to an upper corner of the sheet any See also:flowers, seeds or leaves needed for See also:dissection or microscopical examination, especially where from the fixation of the specimen it is impossible to examine the leaves for oil-receptacles and where See also:seed is See also:apt to See also:escape from ripe capsules and be lost. The addition of a careful dissection of a See also:flower greatly increases the value of the specimen. To ensure that all shall See also:lie evenly in the herbarium the plants should be made to occupy as far as possible alternately the right and See also:left sides of their respective sheets. The species of each genus are then arranged either systematically or alphabetically in See also:separate covers of stout, usually light brown paper, or, if the genus be large, in several covers with the name of the genus clearly indicated in the See also:lower left-hand corner of each, and opposite it the names or reference See also:numbers of the species. Undetermined species are relegated to the end of the genus. Thus prepared,the specimens are placed on shelves or movable trays, at intervals of about 6 in., in an air-tight See also:cupboard, on the inner See also:side of the See also:door of which, as a See also:special See also:protection against insects, is suspended a See also:muslin bag containing a piece of camphor. The systematic arrangement varies in different herbaria. In the great British herbaria the orders and genera of flowering plants are usually arranged according to See also:Bentham and Hooker's Genera plantarum; the species generally follow the arrangement of the most recent See also:complete monograph of the See also:family. In non-flowering plants the See also:works usually followed are for ferns, Hooker and See also:Baker's Synopsis filicum; for mosses, Miiller's Synopsis muscorum frondosorum, Jaeger & Sauerbeck's Genera et species muscorum, and Engler & Prantl's Pflanzenfamilien; for See also:algae, de Toni's Sylloge algarum; for hepaticae, Gottsche, Lindenberg and Nees ab Esenbeck's Synopsis hepaticarum, supplemented by Stephani's Species hepaticarum; for See also:fungi, Saccardo's Sylloge fungorum, and for See also:mycetozoa See also:Lister's monograph of the group. For the members of large genera, e.g. See also:Piper and Ficus, since the number of See also:cosmopolitan or very widely distributed species is comparatively few, a See also:geographical grouping is found specially convenient by those who are constantly receiving parcels of plants from known See also:foreign See also:sources. The ordinary systematic arrangement possesses the great See also:advantage, in the See also:case of large genera, of readily indicating the See also:affinities of any particular specimen with the forms most nearly allied to it. Instead of keeping a See also:catalogue of the species contained in the herbarium, which, owing to the See also:constant additions, would be almost impossible, such species are usually ticked off with a See also:pencil in the systematic See also:work which is followed in arranging them, so that by reference to this work it is possible to see at a glance whether the specimen sought is in the herbarium and what species are still wanted. Specimens intended for the herbarium should be collected when possible in dry See also:weather, care being taken to select plants or portions of plants in sufficient number and of a size adequate to illustrate all the characteristic features of the species. When the See also:root-leaves and roots present any peculiarities, they should invariably be collected, but the roots should be dried separately in an See also:oven at a moderate See also:heat. Roots and fruits too bulky to be placed on the sheet of the herbarium may be conveniently arranged in See also:glass-covered boxes contained in drawers. The best and most effective mode of drying specimens is learned only by experience, different species requiring special treatment according to their several peculiarities. The chief points to be attended to are to have a plentiful See also:supply of botanical drying paper, so as to be able to use about six sheets for each specimen; to See also:change the paper at intervals of six to twelve hours; to avoid contact of one See also:leaf or flower with another; and to increase the pressure applied only in proportion to the dryness of the specimen. To preserve the See also:colour of flowers pledgets of See also:cotton See also:wool, which prevent bruising, should be introduced between them, as also, if the stamens are thick and succulent, as in See also:Digitalis, between these and the corolla. A flower dissected and gummed on the sheets will often retain the colour which it is impossible to preserve in a crowded inflorescence. A See also:flat sheet of See also:lead or some other suitable See also:weight should be laid upon the See also:top of the See also:pile of specimens, so as to keep See also:lip a continuous pressure. Succulent specimens, as many of the Orchadaceae and sedums and various other Crassulaceous plants, require to be killed by See also:immersion in boiling water before being placed in drying paper, or, instead of becoming dry, they will grow between the sheets. When, as with some plants like Verbascum, the thick hard stems are liable to cause the leaves to wrinkle in drying by removing the pressure from them, small pieces of bibulous paper or cotton wool may be placed upon the leaves near their point of See also:attachment to the stem. When a number of specimens have to be submitted to pressure, See also:ventilation is secured by means of frames corresponding in size to the drying paper, and composed of strips of See also:wood or wires laid across each other so as to See also:form a See also:kind of network. Another mode of drying is to keep the specimens in a See also:box of dry See also:sand in a warm-place for ten or twelve hours, and then See also:press them in drying paper. A third method consists in placing the specimen within bibulous paper, and enclosing the whole between two plates of coarsely perforated See also:zinc supported in a wooden See also:frame. The zinc plates are then See also:drawn See also:close together by means of straps, and suspended before a See also:fire until the drying is effected. By the last two methods the colour of the flowers may be well preserved. When the leaves are finely divided, as in Conium, much trouble will be experienced in lifting a See also:half-dried specimen from one paper to another; but the plant may be placed in a sheet of thin blotting paper, and the sheet containing the plant, instead of the plant itself, can then be moved. Thin See also:straw-coloured paper, such as is used for See also:biscuit bags, may be conveniently employed by travellers unable to carry a quantity of
bibulous paper. It offers the advantage of fitting closety to thick- See also:Lichens are generally mounted on sheets of paper of the ordinary stemmed specimens and of rapidly drying. A light but strong
See also:portfolio, to which pressure by means of straps can be applied, and a few quires of this paper, if the paper be changed See also:night and See also:morning, will be usually sufficient to dry all except very succulent plants. When a specimen is too large for one sheet, and it is necessary, in See also:order to show its habit, &c., to dry the whole of it, it may be divided into two or three portions, and each placed on a separate sheet for drying. Specimens may be judged to be thy when they no longer cause a See also:cold sensation when applied to the cheek, or assume a rigidity not evident in the earlier stages of preparation.
Each class of flowerless or cryptogamic plants requires special treatment for the herbarium.
Marine algae are usually mounted on tough smooth See also: This is especially the case with the Ectocarpi, Desmarestiae, and a few others, which should therefore be brought See also:home in a separate See also:vessel. In mounting, the specimen is floated out in a flat white dish containing sea-water, so that foreign See also:matter may be detected, and a piece of paper of suitable size is placed under it, supported either by the fingers of the left hand or by a See also:palette. It is then pruned, in order clearly to show the mode of branching, and is spread out as naturally as possible with the right hand. For this purpose a See also:bone See also:knitting-See also:needle answers well for the coarse species, and a See also:camel's-See also:hair pencil for the more delicate ones. The paper with the specimen is then carefully removed from the water by sliding it over the edge of the dish so as to drain it as much as possible. If during this process part of the fronds run together, the beauty of the specimen may be restored by dipping the edge into water, so as to See also:float out the part and allow it to subside naturally on the paper. The paper, with the specimen upwards, is then laid on bibulous paper for a few minutes to absorb as much as possible of the superfluous moisture. When freed from excess of water it is laid on a sheet of thick white blotting-paper, and a piece of smooth washed See also:calico is placed upon it (unwashed calico,on See also:account of its " facing," adheres to the sea-See also:weed). Another sheet of blotting-paper is then laid over it; and, a number of similar specimens being formed into a pile, the whole is submitted to pressure, the paper being changed every See also:hour or two at first. The pressure is increased, and the papers are changed less frequently as the specimens become dry, which usually takes place in See also:thirty-six hours. Some species, especially those of a thick or leathery texture, See also:contract so much in drying that without strong pressure the edges of the paper become puckered. Other species of a gelatinous nature, like Nemalion and Dudresnaya, may be allowed to dry on the paper, and need not be submitted to pressure until they no longer present a gelatinous See also:appearance. Large coarse algae, such, for instance, as the Fucaceae and Laminariae, do not readily adhere to paper, and require soaking for some time in fresh water before being pressed. The less robust species, such as Sphacelaria scoparia, which do not adhere well to paper, may be made to do so by brushing them over either with See also:milk carefully skimmed, or with a liquid formed by placing See also:isinglass (I oz.) and water (1$ oz.) in a wide-mouthed See also:bottle, and the bottle in a small glue-pot or saucepan containing cold water, See also:heating until solution is effected, and then adding i oz. of rectified spirits of See also:wine; the whole is next stirred together, and when cold is kept in a stoppered bottle. For use, the mixture is warmed to render it fluid, and applied by means of a camel's hair See also:brush to the under side of the specimen, which is then laid neatly on paper. For the more delicate species, such as the Callithamnia and Ectocarpi, it is an excellent See also:plan to place a small fruiting fragment, carefully floated out in water, on a slip of See also:mica of the size of an ordinary microscopical slide, and allow it to dry. The plant can then be at any time examined under the micro-See also:scope without injuring the mounted specimen. Many of the fresh-water algae which form a See also:mere crust, such as See also:Palmella cruenta, may be placed in a vessel of water, where after a time they float like a scum, the earthy matter settling down to the bottom, and may then be mounted by slipping a piece of mica under them and allowing it to dry. Oscillatoriae may be mounted by laying a portion on a See also:silver See also:coin placed on a piece of paper in a See also:plate, and pouring in water until the edge of the coin is just covered. The alga by its own See also:peculiar See also:movement will soon form a radiating circle, perfectly See also:free from dirt, around the coin, which may then be removed. There is considerable difficulty in removing mounted specimens of algae from paper, and therefore a small portion preserved on mica should accompany each specimen, enclosed for safety in a small envelope fastened at one corner of the sheet of paper. Filamentous diatoms may be mounted like ordinary seaweeds, and, as well as all parasitic algae, should whenever possible be allowed to remain attached to a portion of the alga on which they grow, some species being almost always found found parasitical on particular plants. Ordinary diatoms and desmids may be mounted on mica, as above described, by putting a portion in a vessel of water and exposing it to sunlight, when they rise to the surface, and may be thus removed comparatively free from dirt or impurity. Owing to their want of adhesiveness, they are, however, usually mounted on glass as microscopic slides, either in See also:glycerin jelly, See also:Canada See also:balsam or some other suitable See also:medium. size, several specimens from different localities being laid upon one sheet, each specimen having been first placed on a small square of paper which is gummed on the sheet, and which has the locality, date, name of collector, &c., written upon it. This mode has some disadvantages attending it; such sheets are difficult to handle; the crustaceous species are liable to have their surfaces rubbed; the foliaceous species become so compressed as to lose their characteristic appearance; and the spaces between the sheets caused by the thickness of the specimen permit the entrance of dust. A plan which has been found to See also:answer well is to arrange them in cardboard boxes, either with glass tops or in sliding covers, in drawers—the name being placed outside each box and the specimens gummed into the boxes. Lichens for the herbarium should, whenever possible, be sought for on a slaty or laminated See also:rock, so as to procure them on flat thin pieces of the same, suitable for mounting. Specimens on the bark of trees require pressure until the bark is dry, lest they become curled; and those growing on sand or friable soil, such as Coniocybe furfuracea, should be laid carefully on a layer of gum in the box in which they are intended to be kept. Many lichens, such as the Verrucariae and Collemaceae, are found in the best See also:condition during the See also:winter months. In mounting collemas it is advisable to let the specimen become dry and hard, and then to separate a portion from adherent mosses, See also:earth, &c., and See also:mount it separately so as to show the branching of the thallus. Pertusariae should be represented by both fruiting and sorediate specimens. The larger species of fungi, such as the Agaricini and Polyporei, &c., are prepared for the herbarium by cutting a slice out of the centre of the plant so as to show the outline of the cap or pileus, the attachment of the gills, and the See also:character of the interior of the stem. The remaining portions of the pileus are then lightly pressed, as well as the central slices, between bibulous paper until dry, and the whole is then " poisoned," and gummed on a sheet of paper in such a manner as to show the under surface of the one and the upper surface of the other half of the pileus on the same sheet. A " See also:map " of the spores should be taken by separating a pileus and placing it flat on a piece of thin paper for a few hours when the spores will fall and leave a nature See also:print of the arrangement of the gills which may be fixed by gumming the other side of the paper. As it is impossible to preserve the natural See also:colours of fungi, the specimens should, whenever possible, be accompanied by a coloured See also:drawing of the plant. Microscopic fungi are usually preserved in envelopes, or simply attached to sheets of paper or mounted as microscopic slides. Those fungi which are of a dusty nature, and the Myxomycetes or Mycetozoa may, like the lichens, be preserved in small boxes and arranged in drawers. Fungi under any circumstances form the least satisfactory portion of an herbarium. Mosses when growing in tufts should be gathered just before the capsules have become brown, divided into small flat portions, and pressed lightly in drying paper. During this process the capsules ripen, and are thus obtained in a perfect See also:state. They are then pre-served in envelopes attached to a sheet of paper of the ordinary size, a single perfect specimen being washed, and spread out under the envelope so as to show the habit of the plant. For attaching it to the paper a strong See also:mucilage of gum tragacanth, containing an eighth of its weight of spirit of wine, answers best. If not preserved in an envelope the calyptra and operculum are very apt to fall off and become lost. See also:Scale-mosses are mounted in the same way, or may be floated out in water like sea-weeds, and dried in white blotting paper under strong pressure before gumming on paper, but are best mounted as microscopic slides, care being taken to show the stipules. The specimens should be collected when the capsules are just appearing above or in the colesule or calyx; if kept in a damp saucer they soon arrive at maturity, and can then be mounted in better condition, the fruit-stalks being too fragile to See also:bear See also:carriage in a botanical See also:tin case without injury. Of the Characeae many are so exceedingly brittle that it is best to float them out like sea-weeds, except the prickly species, which may be carefully laid out on bibulous paper, and when dry fastened on sheets of white paper by means of gummed strips. Care should be taken in See also:collecting charae to secure, in the case of dioecious species, specimens of both forms, and also to get when possible the roots of those species on which the small granular starchy bodies or gemmae are found, as in C. fragifera. Portions of the fructification may be preserved in small envelopes attached to the sheets. Additional information and CommentsThere are no comments yet for this article.
» Add information or comments to this article.
Please link directly to this article:
Highlight the code below, right click, and select "copy." Then paste it into your website, email, or other HTML. Site content, images, and layout Copyright © 2006 - Net Industries, worldwide. |
|
|
[back] HERB (Lat. herba, grass, food for cattle, generally... |
[next] HERBART, JOHANN FRIEDRICH (1776-1841) |