. Plant anatomy from the standpoint of the development and functions of the tissues, and handbook of micro-technic. Plant anatomy. Fig. 55.—Diagram to show the radial flow of water in pine wood, from the tracheids of the late growth of one year into those of the early growth of the succeeding year. is seen that the pits are plentiful in the slanting common wall between two vertically contiguous tracheids (Fig. 56). Relation of the Tracheal Tissues to the Medullary Rays and Wood Parenchyma.—One of the functions of the medullary rays is to carry radially into the bark water. which they have take
. Plant anatomy from the standpoint of the development and functions of the tissues, and handbook of micro-technic. Plant anatomy. Fig. 55.—Diagram to show the radial flow of water in pine wood, from the tracheids of the late growth of one year into those of the early growth of the succeeding year. is seen that the pits are plentiful in the slanting common wall between two vertically contiguous tracheids (Fig. 56). Relation of the Tracheal Tissues to the Medullary Rays and Wood Parenchyma.—One of the functions of the medullary rays is to carry radially into the bark water. which they have taken on from the tracheal tubes and tracheids. Their other most important function of transporting and storing food will be spoken of in later chapters. Wherever a medullary ray comes into contact with a tracheal tube or tracheid there are pits or thin areas in the common wall separating them through which water and solutes can the more easily pass. And the same condition exists where the wood parenchyma cells come into contact with the tracheal tubes and tracheids. The medullary rays and wood parenchyma are therefore in position to take up and store water, and to assist in its radial and tangential distribution. It has not been demonstrated, and it is indeed doubtful, that the rays and wood parenchyma ' as living tissues assist mate- rially the dead tracheal tissues in the vertical transmission of water. The undoubted use of their intimate relationship, aside from the radial and tangential distribution of water, will be told in subsequent chapters. The Ring of Annual Growth.—The physiological significance of the ring of growth has already been told in the chapter on secondary increase in thickness. Recapit- ulating in a sentence: The large tracheal tubes and tracheids of the early growth provide for the in- creased demand for water, while the predominating wood fibers. Fig. s6.—Diagram indicating by arrows how the water in the tracheids of pine passes longitudinally from
Size: 865px × 2890px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectplantanatomy, bookyea
