CHAPTER II.
CHAPTER II.
COURSE OF THE SAP FROM THE ROOT TO THE LEAF, AND BACK TO THE ROOT.
Jourse of the upward sap through the whole of the wood . The upward sap goes through the heart-wood; proof by experiment And through the sap-wood ; proof by example By what mechanical power is the upward sap raised P Where is the sap elaborated? Whence the new growth 3 in eth
ing deposited ? . , , Sap supposed to be elaborated i in the leaf Growth in girthing supposed to be deposited from this elaborated sap in returning down the bark .
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CONTENTS.
First office of the leaf, transpiration and excretion Leaf supposed by some to absorb the food of plants Errors of Liebig Second office of the leaf, the formation of winter-bud Third office of the leaf, the changing of the sap from the upward conduit, the wood, to the downward conduit, the bark The growth in girthing is from the downward sap, or dependent on it; proof by experiment ; And supposed to be deposited from the bark , , But elaboration certainly takes place before the sap reaches the leaf And also after it quits the leaf , , . , , Received theories of growth in girthing . , ; The pith or medulla, and medullary rays or silver grain . . Medullary rays longitudinal plates, only bounded in length °y the _ height of trees and length of branches and roots . The shake, and cup-shake Lateral as well as longitudinal flow of sap through the whole wood The longitudinal pith-channels extend throughout the tree, from the pith of the original seedling to the finest ramifications of the roots and branches of the largest tree which is entirely alive . Diminution in the size of the pith and its disappearance vulgar errors Whether the pith is the conduit of the upward sap or not Do the central piths of budded buds, of grafts, and of the shoots of coppice-wood, communicate with Dutrochet’s concentrical pins P, Office of the pith unknown As the sap-channels are general, not peeulin, pruning increases the supply to the leader A. new layer of bark is formed. every year That roots have no piths an error There is no ¢rwe circulation of the sap like that of the blood of animals