The operation of _drying_ the specimens has been here described, but that of _mounting_ them on _white_ paper is equally important. Gum Arabic is generally used for this purpose, but it is very bad; does not adhere sufficiently, and thus allows the specimens to spring off from the sheets. Fine glue, prepared in a very thin state, is the best material for fixing the plants. The melted glue should, when very hot, be spread over the specimen carefully with a brush, a sheet of dirty absorbent paper lying beneath the specimen to prevent the glue soiling anything, and then the specimen is to be put down upon the sheet of white paper previously laid out for its reception. A towel is then taken to press the different branches or leaves gently down upon the surface of the paper. After this is done, a few sheets of drying paper are to be laid over the specimen, and on the top of this another sheet of white paper for the reception of another glued specimen, and so on until all are completed. A board is then to be placed over the whole, and a weight, in order to press all parts of the plants equally to the sheets of paper, until they are made firm by the drying of the glue. After the specimens have stood in this manner a few hours, they are to be taken out, their names, localities, and dates written at the bottom of the sheet, and the whole arranged in such manner as the possessor may think proper. Any refractory stems or branches that have sprung up from the paper in spite of the glue, may be fastened down by slips of gummed paper. The marginal portion of postage-stamp sheets supplies these to those who can obtain them in sufficient quantity. The plants of each genus are to be put together inside of a double sheet of paper, with their _generic_ name written at the bottom of the sheet upon the outside at the left hand corner; for instance, the pansy, the sweet violet, the dog violet, the yellow mountain violet, &c., are all to be put inside of one double sheet, the generic name "VIOLA" being written upon the corner of it. This is to facilitate references.