Fig. 181. Alternate leaves, in Linden, Lime-tree, or Basswood.
Fig. 182. Opposite leaves, in Red Maple.
182. The technical name for the attachment of leaves to the stem is the insertion. Leaves (as already noticed, [54]) are inserted in three modes. They are
Alternate (Fig. [181]), that is, one after another, or in other words, with only a single leaf to each node;
Opposite (Fig. [182]), when there is a pair to each node, the two leaves in this case being always on opposite sides of the stem;
Whorled or Verticillate (Fig. [183]) when there are more than two leaves on a node, in which case they divide the circle equally between them, forming a Verticel or whorl. When there are three leaves in the whorl, the leaves are one third of the circumference apart; when four, one quarter, and so on. So the plan of opposite leaves, which is very common, is merely that of whorled leaves, with the fewest leaves to the whorl, namely, two.