1125. With the formation of branches there is at the same time a diminution of the cellular tissue, and an increase of the tracheæ. Entirely new spiral vessels commence in the branches, and are not continued or prolonged into the stalk. The further indeed the extent of the ramification, by so much less is the quantity of cellular tissue, and by so much greater the number of the tracheæ. It comes at last to this, that the tracheal fascicles, which were from all sides surrounded by dense cellular tissue, are only then loosely connected by a thin layer of such substance. This ramuscule is still therefore only a hollow stalk, consisting of fascicles of tracheæ disposed in circles, and so united by a thin cellular integument or membrane, that the whole forms a vesicle. 1126. This vesicle is a _Bud_. A bud is at bottom none other than the end of a twig that has become hollow. 1127. Several buds are usually involved in each other, i. e. many vesicles of tracheal rings have been encased in each other. They issue gradually forth and become shoots or buds. Buds are bulbs at the end of the branches. _Leaves._ 1128. If the bud or the external vesicle ruptures, while the cellular substance becomes consumed at the apex or between two or more tracheal fascicles, it is then manifested as a _leaf_ or _Leaves_. 1129. Then the second vesicle grows forth, becomes petiolated, ruptures and becomes leaf or leaves. In this manner a twig is formed, surrounded in a spiral manner by leaves. 1130. The younger leaves have been originally inclosed in the older, as in their sheaths. 1131. Every perfect leaf, i. e. every leaf-vesicle, must be regarded as the terminal extremity of an entire twig, from or out of the angle of which a new twig grows forth, that again as a bud ruptures, and from which again a twig grows forth. 1132. All leaves therefore range directly opposite to each other. A branch with many leaves is a system of branches, which grow out of each other, like the articular pieces of the grass-culm or straw. 1133. A leaf is a whole plant with all its tissues and systems; with cells, ducts, tracheæ; bark, liber, wood, stalk and branches. The leaf is a tree of special form, a tree, whose branches or tracheal fascicles all lie in one plane and are held together by parenchyma. It is the bodily expression of the position of the tracheal circle in the stem, only ruptured and to the greatest degree attenuated. 1134. In the division of the ribs of the leaf the internal arrangement of the woody fasciculi in the stem has been placed before our eyes, as by the scalpel of an anatomist. 1135. From the arrangement of the ribs of the leaf the structure of the whole plant can be recognized and its character determined. The leaf is the table of contents or index of the stem. 1136. Plants, which have no tracheæ, have also no leaf-ribs--Mosses.