. The essentials of botany. Botany. ZTGOfHTTA. 121 â wHioh 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 {DiatomaoeaB) 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 a
. The essentials of botany. Botany. ZTGOfHTTA. 121 â wHioh 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 {DiatomaoeaB) 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. 65), thus 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- ^^ ^_^^ ^^^^^ ^j^^ ^^ ^ ^^^^ Hoc- tlio-w arpfrpp or showing the overlapping walls; B, lies, tney are iree, or aiiacnea game view of a diatom undergoing fls- , .1 â â ⢠,j.â T,_ i:+â sion; C, side or top view of a diatom to Otner objects Dy utile {Navioula virldisj, showing markings. stalks, and they are frequently '^ ^ â¢*^'" imbedded in a mucous secretion. The free 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 : H. Holt and company, ;
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