LEAP

in botany, is a term applied to various lateral outgrowths of the stem, (e.g.) bracts, sepals, and petals, all of which are considered under their individual headings, but in its best known sense it is applied to those members of the plant which constitute its foliage. The foliage L. consists typically of three parts, the lamina or leaf-blade, petiole or leaf-stalk, and vagina or leaf-base. The vagina frequently bears two lateral outgrowths known as sitpules, (¢.g,) rose; when vagina and petiole are absent, as is often the case, the L. is said to be se ile, (e.g.). honeysuckle. The shape of the lamina varies very greatly, but the different forms are divided sharply into two as compound or simple, the former indicating that the lamina is split up into a number of distinct parts called leaflets, while the latter indicates that however much the blade may be indented it is not split up into leaflets. The venation of L’s. is nece arily related to their form: in the typical L. of a Monocotyledon, (e.g.) iris, the veins run parallel to one another, and the L. is long and undivided, while in a Dicty led on the venation is always reticulate and the L. may be greatly divided, (e.g.) horse-chestnut. The same plant may bear several types of L’s., and one which grows with part of its foliage in a submerged condition will be noticed to have its aquatic L’s. very finely divided to withstand the force of the water. The functions performed by L’s. are of the greatest importance to the life of the parent plant. -Most of the carbon dioxide absorbed from the atmosphere is taken in by the L’s.; respiration or the exchange of carbon dioxide for oxygen is also effected by them, as well as transpiration or the giving off of large quantities of surplus water.