_Preparation of the objects._—The necessary preliminary to the examination of the fibres themselves is their isolation. This is accomplished either by means of the dissecting microscope, or more roughly, according to circumstances. Having obtained the filaments, they are boiled in a 10 per cent. solution of sodium carbonate until sufficiently softened to yield easily to the “teazing” needles. In certain cases the boiling must be supplemented by trituration in a mortar; this, or some similar operation, is especially necessary when the fibres are embedded in a mass of cellular tissue (parenchyma) e. g. in the fibro-vascular bundles of monocotyledons. Sections of the filaments are prepared by cutting in a microtome, the filaments being previously agglutinated into a stiff bundle by means of any of the usual stiffening solutions, and after drying, embedded in wax in the usual way. Sections of fresh stems and tissues are cut with a “section” razor. Having prepared the objects, their examination under the microscope necessarily divides itself into:—(1) the determination of external features; (2) the diagnosis of chemical composition. The fibres themselves will be individually considered in regard to microscopic features. There is one aspect of these structural features, however, which admits of more general treatment, and in respect to this we may anticipate with advantage, viz., the dimensions or simple elements of form. The importance of the determination of the length and diameter of both filaments and fibres will be readily appreciated by an inspection of the following table, in which the numbers are given for several of the more important. A careful study of this table in relation to the application of these several fibres, will show that the correlation of the latter with these ultimate dimensions is close and essential. {39} TABLE OF LENGTHS OF RAW FIBRES (FILAMENTS) AND DIMENSIONS OF CONSTITUENT CELLS AND FIBRES.