Hairs are often covered with curious little branches or protuberances, and present many other peculiarities of form which throw a considerable light upon certain problems in scientific microscopy. Fig. 33 represents a hair of two cells taken from the flower of the well-known dead-nettle, which is remarkable for the number of knobs scattered over its surface. A similar mode of marking is seen in Fig. 31, a club-shaped hair covered with external projections, found in the flower of the Lobelia. In order to exhibit these markings well, a power of two hundred diameters is needed. Fig. 21 shows this dotting in another hair from the dead-nettle, where the cell is drawn out to a great length, but is still covered with these markings. Fig. 20 is an example of a very curious hair taken from the throat of the pansy. This hair may readily be obtained by pulling out one of the petals, when the hairs will be seen at its base. Under the microscope it has a particularly beautiful appearance, looking just like a glass walking-stick covered with knobs, not unlike those huge, knobby club-like sticks in which some farmers delight, where the projections have been formed by the pressure of a honeysuckle or other climbing plant. A hair of a similar character, but even more curious, is found in the same part of the flower of the Garden Verbena (see Fig. 27), and is not only beautifully translucent, but is coloured according to the tint of the flower from which it is taken. Its whole length is covered with large projections, the joints much resembling the antennæ of certain insects; and each projection is profusely spotted with little dots, formed by elevation of the outer skin or cuticle. These are of some value in determining the structure of certain appearances upon petals and other portions of the flowers, and may be compared with Figs. 33 to 35 on Plate III. Fig. 26 offers an example of the square cells which usually form the bark of trees. This is a transverse section of cork, and perfectly exhibits the form of bark cells. The reader is very strongly advised to cut a delicate section of the bark of various trees, a matter very easily accomplished with the aid of a sharp razor and a steady hand. Fig. 24 is a transverse section through one of the scales of a pine-cone, and is here given for the purpose of showing the numerous resin-filled cells which it displays. This may be compared with Fig. 16 of Plate I. Fig. 25 is a part of one of the “vittæ,” or oil reservoirs, from the fruit of the caraway, showing the cells containing the globules of caraway oil. This is rather a curious object, because the specimen from which it was taken was boiled in nitric acid, and yet retained some of the oil globules. Immediately above it may be seen (Fig. 23) a transverse section of the beechnut, showing a cell with its layers of secondary deposit.