The object of using glycerine at all is merely that it has a much lower refractive index than balsam, so that delicate structures may sometimes be better seen in the former medium, but balsam is to be preferred wherever it is possible to use it, _i.e._ almost always. The writer has not mounted a preparation in glycerine or a medium containing it for many years, nor, with proper staining, does he think it can ever be necessary to do so, except in the case of dissections in which the glycerine can be slowly run in without disturbing the arrangement, as spirit would be pretty sure to do. The harder portions of plants, woody stems, shells of fruit, or the like, require different treatment, and must, as a rule, be allowed to dry thoroughly before being cut. Starch granules are somewhat troublesome to mount satisfactorily. The writer has tried many methods, and, on the whole, prefers a glycerin-gelatin medium, which keeps for an almost indefinite time, and may be made as follows: Thirty grains of gelatine (Nelson’s “brilliant” or other transparent gelatine is to be preferred) are allowed to soak in water, and the swollen gelatine is drained, and dissolved in the water which it has absorbed, by the aid of a gentle heat. An equal bulk of pure glycerine is then added. In using, a small portion is transferred to a slide with the point of a knife and melted, a small quantity of starch granules added, and stirred into it with a needle. The cover-glass is then laid up on the still-fluid drop, pressed gently down so that the drop is extended to the margin of the cover, and the whole allowed to cool. It is then to be painted round with several layers of Brunswick black, or Hollis’s glue, or zinc-white cement, to prevent evaporation,--Hollis’s glue being perhaps the best medium for the purpose. Petals, or other parts of which it is desired to obtain a surface view, must be mounted in cells, which may be made by the use of button-moulds of suitable size, cemented to the glass slide with marine glue. The slide must be free from grease, as the tissue must be fixed in position by the use of gum, and allowed to dry thoroughly before closing the cell, or the cover-glass will be bedewed with moisture when the cell is closed. The best plan is, after air-drying for a couple of days, to place the preparation on a metal plate over a beaker of boiling water for an hour or more, and then to close the cell immediately with Brunswick black, maintaining the heat at first to ensure rapid drying, and then slowly withdrawing it. When cool, another coat should be given, and rather thick covers should be used, as these preparations are never required to be examined with high powers.