. The essentials of botany. Botany. 38 THE TISSUES OF PLANTS. Fia. 15.—Tracheary tissue (pitted and tracheids). joining cells is very thin and permeable to water except a button-like thickening, in the center. When seen in surface view, a bordered pit shows a double circle, the smaller inner one being the opening into the pit and the outer circle, the outer edge of the diaphragm. 49. Special mention must be made of the tracheids of Conifers (Spruces, Pines, etc.)- These are shaped and thickened like wood fibers but differ in possessing on their radial faces one or more longitudinal rows of bor
. The essentials of botany. Botany. 38 THE TISSUES OF PLANTS. Fia. 15.—Tracheary tissue (pitted and tracheids). joining cells is very thin and permeable to water except a button-like thickening, in the center. When seen in surface view, a bordered pit shows a double circle, the smaller inner one being the opening into the pit and the outer circle, the outer edge of the diaphragm. 49. Special mention must be made of the tracheids of Conifers (Spruces, Pines, etc.)- These are shaped and thickened like wood fibers but differ in possessing on their radial faces one or more longitudinal rows of bordered pits. They com- bine the functions of tracheids and fibrous tissue, serving both for conduction of water and for mechanical support. 50. Sieve Tissue. In almost all of the higher plants and in many of the more massive lower plants, there are found rows of elongated rather wide cells whose transverse separating walls are pierced by numerous larger or smaller perforations. Where two such cells lie side by side parts of the lat- eral separating wall will often show simi- lar perforated areas. These are the so- called sieve plates which give the name to- this tissue. The walls of the sieve tubes, as the elongated cells are called, are usu- ally rather thin. The sieve plates, on the contrary, are rather thick. In surface view they look like a sort of network. In some cases, the meshes of the net are perforations, in others, they are thin walled areas perforated by several to many fine holes. The mature sieve tubes have the walls lined with a thick layer of cytoplasm in which the nucleus is imbedded. FiQ. 16.—Sieve Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bessey, Charles E. (Charles Edwin), 1845-1915; Bessey, Ernst Athearn, 1877-1957. joint author. New York, H. Holt and company
Size: 1623px × 1539px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublisher, booksubjectbotany
