Elementary botany . nding theentire bundle are small cells with thickwalls. These are elongated and the taper-ing ends overlap. They are thus slender Transection of fibrovascular bundle of and long and form fibers. In such a Ttndian c°rn- \ tt(\ward PeriPhery. °{& stem : g, large pitted vessels; s, spiral bundle all of the cambium has passed vessel; r, annular vessel: /. air cavity formed bv breaking apart of the cells ; /, over into permanent tissue and is said to fc0ft bast, a form of sieve tissue ; /, thin- be closed. walled parenchyma. ( 108. Rise of water in the vessels.—During the
Elementary botany . nding theentire bundle are small cells with thickwalls. These are elongated and the taper-ing ends overlap. They are thus slender Transection of fibrovascular bundle of and long and form fibers. In such a Ttndian c°rn- \ tt(\ward PeriPhery. °{& stem : g, large pitted vessels; s, spiral bundle all of the cambium has passed vessel; r, annular vessel: /. air cavity formed bv breaking apart of the cells ; /, over into permanent tissue and is said to fc0ft bast, a form of sieve tissue ; /, thin- be closed. walled parenchyma. ( 108. Rise of water in the vessels.—During the movement of the water ornutrient solutions upward in the stem the vessels of the wood portion of thebundle in certain plants are nearly or quite filled, if root pressure is activeand transpiration is not very rapid. If. however, on dry days transpirationis in excess of root pressure, as often happens, the vessels are not filled withthe water, but are partly filled with certain gases because the air or other. 54 PHYSIO LOG Y. gases in the plant become rarefied as a result of the excessive loss of are then successive rows of air or gas bubbles in the vessels separatedby films of water which also line the walls of the vessels. The condition ofthe vessel is much like that of a glass tube through which one might pass thefroth which is formed on the surface of soapy water. This forms a chainof bubbles in the vessels. This chain has been called Jamins chain becauseof the discoverer. 109. Why water or food solutions can be raised by the plant to the heightattained by some trees has never been satisfactorily explained. There areseveral theories propounded which cannot be discussed here. It is probablya very complex process. Root pressure and transpiration both play a part,or at least can be shown, as we have seen, to be capable of lifting water to aconsiderable height. In addition to this, the walls of the vessels absorb waterby diffusion, and in the other elements of t
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