Sap
2 of the 6 encyclopedias on this shelf carry an entry for Sap. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
the circulating fluid of plants. Sap is to the plant what blood is to the animal. It courses through passages corresponding to the veins and arteries of an animal. It is like blood in that it consists largely of water, carrying nutritive particles from the ground to the parts of the plant where they are needed. It also circulates through the leaves and other breathing portions of the plants, presenting itself to the influence of the sunlight and of air. Plant life is as dependent upon sap as animal life is dependent upon blood. The analogy between sap and blood may be carried still farther. In addition to blood, the body of an animal may contain other liquids, as saliva and lymph; so, in addition to sap, many plants have special ducts containing liquids other than sap. Turpentine, for instance, is made, not from the sap, but from the contents of the turpentine ducts of the southern pine. Many economic uses are made of sap. The juices of fruits are hoards of concentrated sap; we have sugar and sirups from the sap of the maple and the sugarcane; rubber from the sap of the rubber tree; opium from the sap of the poppy plant; and pulque from the sap of the agave plant. Many gums are the dried sap of corresponding shrubs and trees. See Turpentine ; Maple ; Rubber
Collier's New Encyclopedia (1921)
the nutrimental fluid which circulates in plants. As it rises in the stem it is of a watery nature and contains the various inorganic matters absorbed by the roots, also some sugar, dextrine, and other organic substances which it In has dissolved in its upward course. its passage to the leaves it becomes more and more altered from the state in which it was absorbed by the roots; but when it reaches the leaves it is still unfitted for the requirements of the plant, and the is hence termed crude sap. Through action of the light and air it undergoes changes in the leaves and important other green parts, and becomes adapted for the nourishment of the plant. In this state it is termed elaborated sap. In dicotyledons this elaborated fluid descends through the internal bark and cambium layer toward the root, and is transmitted laterally inward by the medullary rays.
What Has Changed in the Last Century
Aiton's 1910 comparison of sap to blood "coursing through passages corresponding to the veins and arteries" is the part that has not survived: plants have no pump and no circuit. Water and minerals move one way up the dead xylem, pulled by evaporation from the leaves under tension, an explanation proposed by Dixon and Joly in 1894 and now standard; sugars move separately through living phloem, explained by Ernst Münch's pressure-flow model of 1930, which fits Collier's 1921 description of "elaborated sap" descending through the inner bark. Modern botany also separates true sap from the latex of rubber and opium poppy and the resin of pines, which Aiton already sensed were carried in ducts of their own. Maple sap, famously, is driven not by transpiration but by pressure built up in the stem during freeze-thaw cycles in late winter.
Written for this edition, 2026.