1137. Plants, which have only isolated or non-ramifying fascicles of tracheæ, have parallel leaf-ribs that do not ramify--Monocotyledons. 1138. Plants, which have a circle of tracheæ, or rings of wood, have leaves with ramified ribs--reticular leaves or true foliage--Dicotyledons. 1139. The stronger indeed the ramification of the leaf-ribs, by so much the higher is the perfection of the leaf. The lowest leaf is that devoid of ribs, the higher that with parallel ribs, the highest being the reticular-veined leaf. 1140. The number and forms of the leaves that proceed from a bud, depend partly upon the number of tracheal fascicles, which pass out of the ramule into the leaf, partly upon the form of the leaf-bud. 1141. If the bud be simply ruptured at its apex or only between two fascicles of tracheæ, there then originates the spathiform leaf. 1142. If the cellular substance between several tracheal fascicles be consumed by the severing action of light and by the air, then the bud divides into several leaves. 1143. The fundamental form of the leaf is the oviform, because the bud is to be thought of as being round. Through the elongation or compression of the bud, lanciform, cordiform leaves, &c. originate. Besides it appears, that the leaf-buds, at least those of the reticular-veined leaves, burst in a circinate manner, like the ferns, and unroll themselves. Therefore the leaves are unilateral and clasp the stem inferiorly; or the petiole displays its spathiform origin. In this case the leaf is not a part of a hollow globe, but the entire globe, that has ruptured in the transverse direction at the extremity of the petiole. Such is the case at least in the demispathiform leaves of the Umbelliferous plants. 1144. The primary position of the leaves like that of the branches is thus verticillate, yet always, however, under the idea of one being encased within the other. The leaves are here only the ultimate branches. 1145. If the leaves upon the ramules issue from each other, then this happens in the same manner as with the branches. 1146. The verticillate position of the leaves is therefore the lowest, next succeeds the crucial, then the spiriform, and lastly the scattered. 1147. The spathose leaves are only to be regarded as a single bud, and therefore differ from the whorl, in so far as we regard this as the development of several leaves, that have not, however, been extruded from each other. 1148. Divided leaves originate through a higher operation of light. In them the formation of ribs preponderates, and therefore they rank higher than the undivided. 1149. From this cause the pinnate leaves are the highest.