. Nature and development of plants. Botany. 58 STRUCTURE OF THE ROOT a mantle of cells, the root cap. This cap protects the delicate cells within like a thimble so that they are not exposed or injured as the root extends through the soil. At the tip of the root, just within the root cap, the cells are actively dividing and adding new cells to the end of the root and some cells are also added. H Fig. 32. Later stages in the division of the cell: E, the fibrillae pulling the separated halves of the chromosomes to the opposite poles of the spindle. The inner series of fibrillae are now seen at th
. Nature and development of plants. Botany. 58 STRUCTURE OF THE ROOT a mantle of cells, the root cap. This cap protects the delicate cells within like a thimble so that they are not exposed or injured as the root extends through the soil. At the tip of the root, just within the root cap, the cells are actively dividing and adding new cells to the end of the root and some cells are also added. H Fig. 32. Later stages in the division of the cell: E, the fibrillae pulling the separated halves of the chromosomes to the opposite poles of the spindle. The inner series of fibrillae are now seen at the equator between the two groups of chromosomes. F, the chromosomes arranged at the poles and the inner fibrillae increasing in size and number. G, the fibrillae have increased in number until they nearly reach the opposite walls of the mother cell. Their thickening at the equator is the first indication of the wall separating the two new cells. H, position of the new wall clearly indicated.—I. D. Cardiff. to the inner side of the root cap (Fig. 34). Owing to this unique arrangement it does not matter if the outer cells of the cap are injured or destroyed as the root pushes through the soil, because the cap is constantly being renewed from within, and so always furnishes adequate protection to the delicate cells within. The cells that are added to the tip of the root divide several times after their formation, so we find that the tip of the root for a distance of one or two mm. is composed of small cells that are in a process of division but that are enlarging to only a slight degree (Fig. 34). This region is called for this reason the for- mative region of the root. Back of the formative region for a distance of two or four mm. the cells are dividing to a less degree but are elongating very rapidly and changing in form (Fig. 35). This is the region of rapid elongation. Still further back elonga- tion has ceased, but the walls of the cells are becoming thicker. Please note th
Size: 2523px × 990px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublisher, booksubjectbotany
