In a particular kind of Teazle and in a large Sunflower-like Composite (_Silphium laciniatum_) every pair of two opposite leaves run together, so that a little cup-like hollow is formed surrounding the stem, in which water collects. Insects climbing up the stem and trying to get at the heads of flowers fall in and get drowned in this water; their bodies may be seen floating about in it, and probably when these decay, their decay-products are of some use to the plant. This curious contrivance is only a development of a very common arrangement. In most leaves you will find that rainwater is intended to run in a particular direction. There are little grooves and canals down which it is supposed to go, and dry, thirsty hairs may be found so arranged as to intercept part of it. Thus in summer the plants are not confined entirely to the water from the ground, but are also refreshed by the rain from above. But if you look closely along these little channels, and especially at the base of the leaf where they join the stem, you will find that dust particles washed down by the rain collect and form little streaks and patches. The air is full of all sorts of dust particles which are made up of every conceivable substance. Many of these minute grains of dust will be dissolved in the water, and help to supply the plant with food. Nor is that all, for if you take a hand-lens and examine these dust particles very closely, you will very probably find small animalcula moving about. They are not pretty; in fact they are quite horrible to look at. These are tiny mites which live in these places. Their office is probably to eat up everything eatable (including eggs of insects and spores of fungi), and their excreta as well as their own bodies will probably be dissolved in the water and go to help the plants. The most certain place to find them is on the leaves of the lime and other trees in August. On the under side of the leaf little bushes of hairs can be found just where the veins fork. It is necessary to take a pin and stir up these hairs to frighten them out, but when this has been done, the lens will show the disgusting-looking little creatures running hurriedly away. They are no doubt exceedingly annoyed at being disturbed in the midst of their sleep, for they come out and forage for anything eatable at night, retiring for the day into these hairy grottos. The structure of these grottos is very complicated. They are often like little caves with a narrow entrance, and the sleeping chamber is quite within the leaf. A great many trees have these curious mite homes. The insects are generally the colour of the hairs, and are not easy to distinguish.