. Beginners' botany. Botany. 104 BEGLVNERS' BOTANY. Fig ances, and the loss of weight will be noticed (Fig. 127). 98. Cut a winter twig, seal the severed end with wax, and allow the twig to he several days; it shrivels. There must be some upward movement of water even in winter, else plants would shrivel and die. 99. To illustrate sap pressure. The upward movement of sap water often takes place under considerable force. The cause of this force, known as root pressure, is not well understood. The pressure varies with different plants and under different conditions. To illustrate: cut off a stro
. Beginners' botany. Botany. 104 BEGLVNERS' BOTANY. Fig ances, and the loss of weight will be noticed (Fig. 127). 98. Cut a winter twig, seal the severed end with wax, and allow the twig to he several days; it shrivels. There must be some upward movement of water even in winter, else plants would shrivel and die. 99. To illustrate sap pressure. The upward movement of sap water often takes place under considerable force. The cause of this force, known as root pressure, is not well understood. The pressure varies with different plants and under different conditions. To illustrate: cut off a strong-growing Hj-^J small plant near ' the ground. By means of a bit of rubber tube attach a glass tube with a bore of approxi- mately the diame- ter of the stem. Pour in a little water. Observe the rise of the water due to the pressure from be- low (Fig 128). Some plants yield a large amount of water under a pressure sufficient to raise a column several feet; others force out httle, but under consider- \ able pressure (less easily de- monstrated). The vital pro- 'f^^-^^""''^^ cesses {, the life processes). 100. The pupil having studied roots, stems, and leaves, should now be able to de- scribe the main vital functions of plants : what is the root func- tion? stem function? leaf function? 101. What is meant by the " sap "? 102. Where and how does the plant secure its water? oxygen? car- bon? hydrogen? nitrogen? sulfur? potassium? 126. — To ILLUSTRATE Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bailey, L. H. (Liberty Hyde), 1858-1954. New York, The Macmillan company
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