Fig. 12 is a hair of the tobacco leaf, exhibiting the two-celled gland at the tip, containing the peculiar principle of the plant, known by the name of “nicotine.” The reader will see how easy it is to detect adulteration of tobacco by means of the microscope. The leaves most generally used for this purpose are the dock and the cabbage, so that if a very little portion of leaf be examined the character of the hairs will at once inform the observer whether he is looking at the real article or its substitute. Fig. 15 is a hair from the flower of the common yellow snapdragon, which is remarkable for the peculiar shape of the enlarged extremity, and for the spiral markings with which it is decorated. Fig. 16 is a curious little knobbed hair found upon the moneywort, and Fig. 17 is an example of a double-knobbed hair taken from the Geum. Fig. 34 affords a very curious instance of a glandular hair, the stem being built up of cells disposed in a very peculiar fashion, and the extremity being developed into a beautiful rosette-shaped head. This hair came from the Garden Verbena. Curiously branched hairs are not at all uncommon, and some very good and easily obtained examples are given on Plate II. Fig. 28 is one of the multitude of branched hairs that surround the well-known fruit of the plane-tree, the branches being formed by some of the cells pointing outward. These hairs do not assume precisely the same shape; for Fig. 29 exhibits another hair from the same locality, on which the spikes are differently arranged, and Fig. 30 is a sketch of another such hair, where the branches have become so numerous and so well developed that they are quite as conspicuous as the parent stem. One of the most curious and interesting forms of hair is that which is found upon the lavender leaf, and which gives it the peculiar bloom-like appearance on the surface. This hair is represented in Figs. 40 and 41. On Fig. 40 the hair is shown as it appears when looking directly upon the leaf, and in Fig. 41 a section of the leaf is given, showing the mode in which the hairs grow into an upright stem, and then throw out horizontal branches in every direction. Between the two upright hairs, and sheltered under their branches, may be seen a glandular appendage not unlike that which is shown in Fig. 16. This is the reservoir containing the perfume, and it is evidently placed under the spreading branches for the benefit of their shelter. On looking upon the leaf by reflected light the hairs are beautifully shown, extending their arms on all sides; and the globular perfume cells may be seen scattered plentifully about, gleaming like pearls through the hair-branches under which they repose. They will be found more numerous on the under side of the leaf.