|Standard Cyclopedia of Horticulture|
Herbarium. An herbarium is a collection of dried plants systematically named, and arranged in cases for ready reference and protection. In the study of systematic botany such collections have existed for many years, and they are an absolute necessity to the student, supplementing field work. Indeed, without an herbarium, scientific systematic work would be practically impossible, for the identification of species, the study of the plants of any given area and the comparison of the flora of different regions can be conducted thoroughly only where specimens of the plants under consideration are at hand and can be readily consulted. Type specimens of new species are deposited in herbaria, and reference is constantly being made to these types to settle the identity of species when meager descriptions only are available. Floras of distant regions have been written by those who have never visited the places, but have worked on the collections that have been brought back. It is only through such collections of dried plants that publications of the plants of a region are possible. It is a vital supplement to actual work in the field. Large and important herbaria exist at many centers of botanical activity in this country and abroad, while private collections are countless.
There are few collections of pressed specimens of plants embracing the wide range of horticulture, and there should be more of them. The advantage of such herbaria in identifying plants under cultivation and in comparing the many forms that are constantly being evolved, and that do not occupy a place in collections of native plants, must be obvious to everybody. Every horticulturist should have' a good herbarium, for it increases very largely the value of his work besides giving much pleasure in the preparation and use of it.
It is like a reference library and it enables a nurseryman to keep his stock true to name. One of the most difficult problems for a systematic botanist or a horticulturist to meet is that of nomenclature, and much trouble and waste time can be avoided by having at hand an authentically named collection, embracing as many forms as possible. A good working herbarium can be made by pressing the cultivated plants at hand and by securing from others specimens of additional forms.
In collecting plants for the press it must be remembered that they are to be mounted on paper ll ½ by 16 3/8 inches in size. These are standard dimensions. Take up small plants by the roots, and of larger plants secure a branch that will show typical leaves and flower or fruit according to what is desired. Note with each plant, on a label or on a tag slipped on the end of the stem, the important characters that are to be entered on the final label, such as trade name, color of flowers, whether it is annual, biennial or perennial, date, locality, collector, and so on. These should be kept carefully with the plant.
The specimens are then laid for pressing between sheets of unsized paper that will readily absorb the moisture. Newspaper will do, but prepared sheets can be bought at very small cost of any botanical dealer, from whom also can be obtained collecting-boxes, trowels, presses and all other details used in making an herbarium. Plants can be folded once or even twice to be adapted to the size of the sheet, unless too many leaves overlap, in which case two specimens, or even more, can be made of the same plant and pressed separately. A little skill will enable one to lay out his plants artistically, showing upper and under surfaces of the leaves, and the various sides of the flowers. Sometimes it is best to section a thick stem or root. The folder with its inclosed plant or plants and accompanying data is then put between driers, which are sheets of a heavy felt paper, very absorbent. On this is placed another folder, and so on until a pile a foot or more high is reached. This pile is then placed in a press. The best kind of press is a simple, portable one, composed of two frames, each made of strips of hard wood arranged at right angles to each other. The press is then tightened by strong straps. The driers should be changed daily for a few times, and the specimens examined, and then less frequently till they are perfectly dry. Most excellent results in quick drying can be secured by means of sheets of corrugated card board with one side flat. (See J. F. Collins, Rhodora xii. 221, 1910). By placing a sheet between the various driers each plant is isolated from its neighbors, and the circulation of air through the pores speedily dries the plants. Put the press in the sun when possible. The old- fashioned method of using plain boards and a heavy weight on top is not to be recommended.
The specimens should then be mounted on sheets of stiff, white, calendered paper, 11 ½ by 16 3/8 inches, eighteen pounds to the ream being standard weight. This is for a perfectly appointed herbarium. The plants can be kept in the original folders and filed in that way, but, for safety and ease in handling, the specimens should be properly secured to the sheets. The regular method is by gluing them down, fish glue being used, and supplementing this with strips of gummed paper, surgeon's isinglass plaster being the best material. These strips are put over portions of the plant that are liable to separate from the sheet. In some large herbaria gummed strips are used entirely. Each mounted sheet must contain but one species, variety or form, but two or more different collections may be on a single sheet. A label accompanies each collection composed of one or more specimens. A convenient size is 3 ½ by 1 ¾ inches. On it should be written the name, locality, date, collector and any useful data such as have been mentioned above.
The mounted sheets are put loose into genus covers of stiff manila paper, 16 ½ by 11 7/8 inches, each cover devoted to a single genus. The name of the genus is written in the lower left-hand corner, and that of the species in the lower right-hand corner. More than one species of the same genus can be put into the same cover. These covers are placed systematically in the herbarium case fitted with pigeon-holes wide and deep enough to hold the covers easily and 6 inches between shelves. The doors must close tightly to keep out insects and dust. The cases are of varying heights, according to convenience, and are generally of wood. The most approved have two rows of about thirteen pigeon-holes each, and are made of steel, thus securing absolute safety.
An herbarium was called "Hortus siccus," or dry garden, by the ancients, but, although in one sense true, it does not convey the correct idea. To the true scientific lover of plants, whether botanist, horticulturist, florist, or nurseryman, a carefully equipped collection of dried plants is not only a great and necessary aid, but a true delight. In them he sees the living plants that they represent, and to dissect a flower, however old it may be, he has but to boil it for a few seconds in a retort, and it can be as easily dissected as if fresh.