. The essentials of botany. Botany. ZTOOPHYTA. 121 which it does by bursting its wall and dividing its con- tents into two parts, each of which finally becomes a new desmid {g, h, i). 254. The Diatoms {Diatomacem) are microscopic uni- cellular water-plants, resembling the Desmids, but differ- ing from them in having walls which are silicified, and in the chlorophyll being hidden by the presence of a yellow coloring matter (phycoxanthine). Each cell is usually composed of two similar portions, called the valves. Each valve may be described as a disk whose edge is turned down all around, so as t
. The essentials of botany. Botany. ZTOOPHYTA. 121 which it does by bursting its wall and dividing its con- tents into two parts, each of which finally becomes a new desmid {g, h, i). 254. The Diatoms {Diatomacem) are microscopic uni- cellular water-plants, resembling the Desmids, but differ- ing from them in having walls which are silicified, and in the chlorophyll being hidden by the presence of a yellow coloring matter (phycoxanthine). Each cell is usually composed of two similar portions, called the valves. Each valve may be described as a disk whose edge is turned down all around, so as to stand at right angles to the remainder of the surface, making the valve have the general plan of a pill-box cover. The two valves are generally slightly different in size, so that one slips within \^% the other {A, Fig. 55), thus ^N forming a box with double sides. In other cases the valves are simply opposed and do not overlap. 255. The individuals may exist singly or in loose fami- lies ; they are free, or attached to other objects by little stalks, and they are frequently imbedded in a mucous secretion, O. Fig. 55.—^, front view of a diatom, showing the overlapping walls; B, same view of a diatom undergoing fis- sion ; C, side or top view of a diatom (Navicula viridis), showing markiugs. Highly magnified. The fi'ee forms are loco- motive, and may be seen in constant motion under the microscope: the mechanism of the motion is not certainly 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. New York, Holt
Size: 1107px × 2258px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1884
