This section is from the book "Sub-Alpine Plants Or Flowers Of The Swiss Woods And Meadows", by H. Stuart Thompson. Also available from Amazon: Sub-Alpine Plants: Or, Flowers of the Swiss Woods and Meadows.
Common blotting-paper should never be used for drying plants in; it is too tender, it does not last, costs too much, and the plants often stick to it. Any coarse, stout, and unsized paper will do, and even old newspapers may be used as a last resort. It is not necessary to buy the specially made grey, absorbent paper, though as it lasts a lifetime it is not expensive in the end. Such drying-paper is supplied in four sizes by Messrs. West, Newman, and Co., of 54, Hatton Garden, London, at 1s. 1d. per quire or 15s. a ream for the smallest size, which measures 16 x 10 inches when folded-Suitable paper cannot always be bought in Swiss resorts, and if the stock has run short it is better to ask the stationer for some of his ordinary rough wrapping-paper. In Italy and France the tough, yellow or grey paper frequently used in grocers' shops will form quite a good drying-paper.
Before the specimens are placed in the press they should be examined, and any superfluous branches, leaves, or buds removed, if a fairly flat object cannot be otherwise attained. Roots should have soil or sand shaken from them, and they should be washed if necessary, and dried in a duster. The plant is then laid out as naturally as possible on a sheet of drying-paper, and others are placed by it until the sheet is fairly covered. Several sheets of paper should be placed between this lot and the next, according to the nature of the plants and the thickness of the paper; but the great idea in pressing plants is to dry them quickly, and thus preserve the colour as naturally as possible. The more paper used and the oftener it is changed and dried the better. At first the papers should be dried every day, in the sun or by the fire; afterwards less often. If the paper is hot, all the better, and a hot iron is often a useful adjunct. The pressure should be light at first, and increased after the first day, but the flowers and delicate leaves of some plants will shrivel if the pressure is not even and adequate. However, many a youthful collector is apt to forget that drying is the chief thing, and that the pressure can be easily overdone.
At the first changing of papers the specimens can be rearranged while pliable, and superabundant parts removed with scissors. Any stems with broken or ragged ends should also be cut clean. When quite fresh many specimens do not so easily yield to necessary treatment as now.
Generally it is better to leave plants in the tin, rather than put them in water, if it is inconvenient to press them within one or two days, while many small kinds would remain fresh a week in the tin if in a cool place, though both leaves and flowers might lose some colour during that time. Most of the very thick or fleshy portions of plants, such as the head of a thistle, the bulb of a Daffodil, or the stem of an Orobanche, should be cut in two before being dried. In fact, the whole of a thick Orobanche or of a plant like Campanula thyrsoidea had better be split in two from top to bottom. Usually both halves are worth preserving. Woody stems also are better split in two, or at any rate thinned.
In order to aid the drying of any such thick or fleshy plants or portions of plants, it is well to make pads of cotton-wool and place them both above and below the specimens. Cotton-wool can be bought in long sheets and easily cut with scissors the size of the drying-paper. It is better that the plants should not touch the cotton-wool itself; but useful and more or less permanent pads can very quickly be made by loosely stitching together with a needle and thread a pair of folded sheets of drying-paper with the wool inside.
Many succulent plants such as Orchids, Lilies, Sedums, and Sempervivums can be dried with the help of these pads, but it is best first to dip them in boiling water up to the base of the flowers. This kills the plant at once, and enables it to be dried more quickly, and with much less loss of colour. Thick Orchids should always be killed in this way, and their tubers and stems might first be pricked with the point of a knife to hasten the process of scalding, for the final result, particularly in regard to the green colour of the leaves, makes it well worth the trouble. Dipping in boiling water is also recommended in the case of Heaths, which shed their leaves while being dried.
With the help of the notebook or diary already referred to, it is well to write on a rough, temporary label the name of the plant, if known, the place where it came from, date, and approximate altitude. It is interesting sometimes to add the kind of soil or geological formation. These labels should be placed with the specimens they refer to, and afterwards copied when the plants are mounted. If a series of one species or variety, especially when belonging to a critical genus, be collected, every example should have a little label or ticket with the same number, while one label only need have the full particulars.
When the specimens are quite dry and stiff they can be packed close together, with only a single sheet of paper between each layer, and this paper need not be absorbent, but if it is unglazed the specimens will keep in position better when travelling, and not slip about so readily if the parcel is not quite tight.