Collect samples of all parts of the plant, — lower and upper leaves, stem, flowers, fruit, and in most cases roots. In small species, those two feet high or less, the whole plant should be taken. Of larger plants, take parts about a foot long. Press the plants between papers or " driers." These driers may be any thick porous paper, as blotting-paper or carpet-paper, or, for plants that are not succulent or very juicy, newspapers in several thicknesses may be used. It is best to place the specimens in sheets of thin paper — grocer's tea paper is good — and place these sheets between the driers. Many specimens can be placed in a pile. On top of the pile place a short board and a weight of thirty or forty pounds, or a lighter weight if the pile is small and the plants are soft. Change the driers every day. The plants are dry when they become brittle, and when no moisture can be felt by the fingers. Some plants will dry in two or three days, while others require as many weeks. If the pressing is properly done, the specimens will come out smooth and flat and the leaves will usually be green, although some plants always turn black in drying.

Specimens are usually mounted on single sheets of white paper of the stiffness of very heavy writing paper or thin bristol-board. The standard size of sheet is ll1/2 by 161/2 inches. The plants may be pasted down permanently and entirely to the sheet, or they may be held on by strips of gummed paper. In the former case, Denison's fish-glue is a good gum to use. Only one species or variety should be placed on a sheet. Specimens that are taller than the length of a sheet should be doubled over when they are pressed. The species of a genus are collected into a genus cover. This cover is a folded sheet of heavy manila or other firm paper, and the standard size, when folded, is 12 by 161/2 inches. On the lower left-hand corner of this cover the name of the genus is written. A label should accompany each specimen upon the separate sheets, recording the name, date of collecting, name of the collector, and any notes that may be of interest. 2n

The specimens are now ready to be filed away on shelves in a horizontal position. If insects attack the specimens, they may be destroyed by fumes of bisulfid of carbon (see page 293) or chloroform. The bisulfid treatment is probably the best yet devised, particularly for large herbaria. In this case it is necessary to place the specimens in a tight box and then insert the liquid. Lumps of naphthalin placed in the cabinet are useful in keeping away insects.

Various poisons have been used on herbarium plants. At one time, the Gray Herbarium used an arsenic solution, but this proved to be injurious to curators. Three corrosive sublimate (bichloride of mercury) recipes are as follows: —

1.  Place as much corrosive sublimate in alcohol as the liquid will dissolve. Apply with a brush, or dip the plants before they are mounted and dry them between sheets. A common method.

2.  Dissolve 13/4 ounces of corrosive sublimate in one pint of alcohol ; add 21/2 fluid drams of carbolic acid, and apply with a paint brush.

3.  One pound of corrosive sublimate, one pound of carbolic acid, to 4 gallons of wood alcohol.

Preserving, Printing, and Imitating Flowers and Other Parts of Plants

To Preserve the Color of Dried Flowers. — 1. Immerse the stem of the fresh specimen in a solution of 32 parts by weight of alum, 4 of niter, and 186 of water for two or three days until the liquid is thoroughly absorbed, and then press in the ordinary way, except that dry sand is sifted over the specimen and the packet submitted to the action of gentle heat for twenty-four hours.

2.  Make a varnish composed of 20 parts of powdered copal and 500 parts of ether, powdered glass or sand being used to make the copal dissolve more readily. Into this solution the plants are carefully dipped ; then they are allowed to dry for ten minutes, and the same process is repeated four or five times in succession.