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| ves have blades with pinnate venation (where major veins diverge from one large mid-vein and have smaller connecting networks between them). Less commonly, dicot leaf blades may have palmate venation (several large veins diverging from petiole to leaf edges). Finally, some exhibit parallel venation. Monocot leaves in temperate climates usually have narrow blades and usually parallel venation converging at leaf tips or edges. Some also have pinnate venation. Arrangement on the stem Main article: Phyllotaxis The arrangement of leaves on the stem is known as phyllotaxis. A large variety of phyllotactic patterns occur in nature: The leaves on this plant are arranged in pairs opposite one another, with successive pairs at right angles to each other (decussate) along the red stem. Note the developing buds in the axils of these leaves. The leaves on this plant (Senecio angulatus) are alternately arranged. Alternate One leaf, branch, or flower part attaches at each point or node on the stem, and leaves alternate direction—to a greater or lesser degree—along the stem. Basal Arising from the base of the plant. Cauline Attached to the aerial stem. Opposite Two leaves, branches, or flower parts attach at each point or node on the stem. Leaf attachments are paired at each node. Decussate An opposite arrangement in which each successive pair is rotated 90° from the previous. Whorled, or verticillate Three or more leaves, branches, or flower parts attach at each point or node on the stem. As with opposite leaves, successive whorls may or may not be decussate, rotated by half the angle between the leaves in the whorl (i.e., successive whorls of three rotated 60°, whorls of four rotated 45°, etc.). Opposite leaves may appear whorled near the tip of the stem. Pseudoverticillate describes an arrangement only appearing whorled, but not actually so. Rosulate Leaves form a rosette. Rows The term distichous literally means two rows. Leaves in this arrangement may be alternate or opposite in their attachment. The term 2-ranked is equivalent. The terms tristichous and tetrastichous are sometimes encountered. For example, the "leaves" (actually microphylls) of most species of Selaginella are tetrastichous bu |