. Foundations of botany. betweenthem). Water travels upward through theducts and through the wood-cells in theregion marked ir. Water with dissolvedplant-food travels downward through thesieve-cells in the region marked s. 76, and covered with anear the upper edge ofthe stripped portion,^and this would seem toprove that such stemssend their building ma-terial — the elaboratedsap — largely at any ratedown through the course is undoubt-edly for the most partthrough the sieve-cells(Figs. 63, 64), which areadmirably adapted toconvey liquids. In ad-dition to these generalupward and downwar
. Foundations of botany. betweenthem). Water travels upward through theducts and through the wood-cells in theregion marked ir. Water with dissolvedplant-food travels downward through thesieve-cells in the region marked s. 76, and covered with anear the upper edge ofthe stripped portion,^and this would seem toprove that such stemssend their building ma-terial — the elaboratedsap — largely at any ratedown through the course is undoubt-edly for the most partthrough the sieve-cells(Figs. 63, 64), which areadmirably adapted toconvey liquids. In ad-dition to these generalupward and downwardmovements of sap, theremust be local transfers laterally through the stem, andthese are at times of much im-portance to the plant. Since the liquid building mate-rial travels straight down the , ., p ii i —Unequal Growth of Rings stem, that side OI the stem on of wood in nearly Horizontalwhich the manufacture of such stem of a juniper. (Natural size.) material is going on most rapidly should grow 1 This may be made the subject of a protracted class-room shoots of willow should be used for the purpose. LIVING PARTS OF THE STEM 111 Plant-food is made out of the raw materials by the leaves,and so the more leafy side of a tree forms thicker ringsthan the less leafy side, as shown in Fig. 79. 119. Rate of Movement of Water in the Stem. — Thereare many practical difficulties in the way of ascertainingexactly how fast the watery sap travels from the root tothe leaves. It is, however, easy to illustrate experimen-tally the fact that it does rise, and to give an approximateidea of the time required for its ascent. The best experi-ment for beginners is one which deals with an entireplant under natural conditions. EXPERBIEXT XXII Wilting and Recovery. — Allow a fuchsia or a hydrangea ^ whichis growing in a flower-pot to wilt considerably for lack of water it freely and record the time required for the leaves tobegin to recover t
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectplants, bookyear1901
