. A manual of botany. Botany. THE VEGETABLE CELL 287 A different view of the composition of the cell-wall has been advanced in recent years by ^\'iesner. He holds that the sub- stance of cell-wall as it is first formed consists of rows of granular bodies which he terms dermatosomcs, which are united together and surrounded by protoplasm. On this hypothesis the cell-wall is living while young and growing. The protoplasm Fig. 616. Fig. 617. Fig. 618. Fig. Ftcr. 616. Eouaded cells. Elliptic or oblong cell. «, 619. Polygonal cells in combination : those of the latter figure be
. A manual of botany. Botany. THE VEGETABLE CELL 287 A different view of the composition of the cell-wall has been advanced in recent years by ^\'iesner. He holds that the sub- stance of cell-wall as it is first formed consists of rows of granular bodies which he terms dermatosomcs, which are united together and surrounded by protoplasm. On this hypothesis the cell-wall is living while young and growing. The protoplasm Fig. 616. Fig. 617. Fig. 618. Fig. Ftcr. 616. Eouaded cells. Elliptic or oblong cell. «, 619. Polygonal cells in combination : those of the latter figure being pitted. thus exists between particles of cellulose, and holds water in its substance. As the cells grow there is a continuous formation of cellulose, due, like its first formation, to the vital activity of the protoplasm. By irregularity of growth, due to internal causes bringing about greater possibility of stretching in certain places, cells become of various forms ; when the growth is uniform, or nearly so, in all parts of the cell-wall, we have a spherical or rounded cell ( 616); but when it is greater at the two extremities than at the sides, the form is oval or oblong [fig. 617). In the above cases, also, the cells are almost, or entirely, free from external pres- sure. But, under other cir- FlG. 620. Fig. 621. cumstanoes, m consequence of the mutual pressure of surrounding cells, they as- sume a polygonal form (figs. 618 and 619), the number of the angles depending upon the mimber and arrangement of the contiguous cells. When the growth is nearly uniform on all sides of the cell- wall, but not equally so at all points of its surface, we have cells which maintain a rounded form in the centre, but have rays projecting from them in various directions, by which they <3 I' 620. Stellate cells. «,/. 621. Cylin- drical cells. The small rounded body in the interior of three of these cells is the Please note that these images are extracted from scanned
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