52. The proper season for the commencement of the study of Botany in schools is in late winter, at the opening of the first session or term after New-Years. The class will thus be prepared before hand by a degree of acquaintance with first principles, for the analysis of the earliest spring flowers - the sweet Epigaea, Anemone, Erigenia or spring beauty, of the North, the yellow jessamine, Chaptalia, or Cryso-gonum of the South, the blood-root and violet every where.
53. Specimens of leaves, stems, roots, fruit, flowers, etc, in unlimited supply are requisite during the whole course. In the absence of the living, let the dried specimens of the herbarium be consulted. Crayon sketches upon the black-board, if truthful, are always good for displaying minute or obscure forms. In the city, classes in Botany may employ, at small expense, a collector to supply them daily with fresh specimens from the country. Moreover, the gardens and conservatories will furnish to such an abundant supply of cultivated species for study and analysis, with almost equal advantage; since the present work embraces, together with the native flora, all exotics which are in any degree common in cultivation.
54. An herbarium (h. s., hortus siccus, dry garden), is a collection of botanic specimens, artificially dried, protected in papers and systematically arranged. Herbaria are useful in many ways; (a.) for preserving the knowledge of rare, or inaccessible, or lost species; (b.) for exchanges, enabling one to possess the flora of other countries: (c.) for refreshing one's memory of early scenes and studies; (d.) for aiding in more exact researches at leisure; (e.) for the comparison of species with species, genus with genus, etc.
55. For collecting botanic specimens, a strong knife for digging and cutting is needed, and a close tin box eighteen inches in length, of a portable form. Enclosed in such a box, with a little moisture, specimens will remain fresh for a week.
56. Specimens for the herbarium should represent the leaves, flowers and fruit, and, if herbaceous, the root also. Much care is requisite in so drying them as to preserve the natural appearance, form and color. The true secret of this art consists in extracting the moisture from them by pressure in an abundance of dry. bibulous paper, before decomposition can take place.
57. The drying press, to be most efficient and convenient, should consist of a dozen quires of ordinary blotting paper, at least 11 x 14 inches, two sheets of wire gauze, (same size) as covers, stiffened by folded edges, and three or four leather straps a yard in length, with buckles. When in use suspend it in the wind and sunshine. In such a press, the specimens dry well in fair weather without once changing. If boards be used for covers instead of wire-gauze, the papers must be changed and dried daily.
58. Succulent plants may be immersed in boiling water before pressing, to hasten their desiccation.
59. The lens, either single, double, or triple, is almost indispensable in the ordinary pursuits of Morphology or Phytography. In viewing minute flowers or parts of flowers the use of the lens can not be too highly appreciated. For dissection with the lens, a needle inserted in a handle, a penknife and tweezers are required. The dried flowers of the herbarium need to be thrown into boiling water before dissection.
60. The compound microscope is undoubtedly a higher aid in scientific investigation than any other instrument of human invention. It is like the bestowment of a new sense, or the opening of a new world. Through this, almost solely, all our knowledge of the cells, the tissues, growth, fertilization, etc, is derived. The skillful use of this noble instrument is itself an art which it is no part of our plan to explain. For such information the student is referred to the works of Carpenter and Quekett
61. On the preparation of botanical subjects for examination we remark briefly. The field of view is necessarily small, and only minute portions of objects can be seen at once. The parts of it are to be brought under inspection successively by the movements of the stage.
62. The tissues of leaves, etc, are best seen by transmitted light. They are to be divided by the razor or scalpel into extremely thin parings or cuttings. Such cuttings may be made by holding the leaf between the two halves of a split cork. They are then made wet and viewed upon glass. The stomata are best seen in the epidermis stripped off; but in the sorrel leaf (Oxalis Violacea) they appear beautifully distinct (§678, Fig. 585,)upon the entire leaf.
63. Woody tissues, etc, may be viewed either as opaque or transparent. Sections and cuttings should be made in all directions, and attached to the glass by water, white of egg, Canada balsam. To obtain the elementary cells separately for inspection, the fragment of wood may bo macerated in a few drops of nitric acid added to a grain of chlorate of potassa. Softer structures may be macerated simply in boiling water.
64. Certain reagents are applied to the softer and more recent tissues to effect such changes in the cell contents, of either color or form, as shall render them visible. Thus sulphuric acid coagulates the primordial utricle (§ 645); a solution of iodine turns it blue j sugar and nitric acid change it to red.