1383. The saps ascend upwards, and chiefly indeed, in the liber; on its passage different substances forming from it, which appear especially in the fruit in greatest proportion and variety.
2. Processes.
1384. The tissues of plants form three formations, which must be similar in their functions, and can only exhibit subordinate differences. The cell-formation is displayed in the cellular tissue, in the bark and root. The vascular formation in the vascular tissue, in the liber and stalk. The tracheal formation in the tracheal tissue, the wood and the leaves. There can accordingly be only three principal functions in the vegetable stem, and of these each will display minor differences.
A. Cellular Processes.
a. ROOT-PROCESS—ABSORPTION.
1385. As the root is the cellular organ proper, so in it principally resides the water-process or the commencement of chemical elaboration and analysis. Now the chemism in an organic body is called digestion.
1386. The root is the mouth or pharynx of the plant, and is therefore principally concerned with absorption. Its process is therefore the formation of mucus, or as it were of salivation. The root cannot, however, create mucus, as it was created at the conclusion of the earth-metamorphosis in the sea; it can absorb it or in the highest degree compound it out of the constituent parts.
1387. The process of the formation of mucus is a process of putrefaction; the function of the root consists accordingly in supporting a constant process of putrefaction. The soil in which the root stands must contain substances susceptible of, and the conditions necessary to, putrefaction. These substances are organic matters and water; the conditions heat and access of air. Such a soil is called humus or mould. In a pure, dry earth, no root can thrive.
1388. Carbon, from its being the earthy body, is the principal one in the formation of mucus, and the basis also of the vegetable bodies. A root can develop itself, if it stand only in a soil such as the calcareous, which contains carbon and water. The calcareous soil is as it were an original mould. It is probable that the calcareous earth is constantly decomposed by the root and its carbon absorbed. The calcareous earth is again neutralized by the carbonic acid of the water and air.
1389. There can be no doubt that the root also abstracts carbon from these elements, and converts it into mucus, or probably separates it from carbonic acid. The mucus approximates the animal nature, so that the root in its constituent parts, in its smell, and even in its structure, exhibits animal properties; animal substances therefore are also the best nutritive media of plants.