. Nature and development of plants. Botany. lyo STRUCTURE OF DIATOMS chains, while others are imbedded in a gelatinous mass of a more or less regular form (Fig. 94, D). The cells are covered by two valves, one of which overlaps the other like the cover of a box. Therefore a diatom presents two quite distinct ap- pearances—the top or valve view and the side or girdle view (Figs. 96, 97). This difference is further intensified by the sculpturing of fine lines that appear upon the walls. An inter- esting feature about these valves is the fact that they are com-. FlG. 97. Structure of Cymbella. in
. Nature and development of plants. Botany. lyo STRUCTURE OF DIATOMS chains, while others are imbedded in a gelatinous mass of a more or less regular form (Fig. 94, D). The cells are covered by two valves, one of which overlaps the other like the cover of a box. Therefore a diatom presents two quite distinct ap- pearances—the top or valve view and the side or girdle view (Figs. 96, 97). This difference is further intensified by the sculpturing of fine lines that appear upon the walls. An inter- esting feature about these valves is the fact that they are com-. FlG. 97. Structure of Cymbella. ing the difference of the two sides of the diatom —After Pfitzer. valve view. B, cross-section show- C, the two girdle views. pletely infiltrated with silica, a substance resembling glass. If a diatom is burned in a flame on a strip of platinum or placed in acid to remove the organic substance the appearance of the valves remains unchanged. The glass-like valves are quite transparent and it can be readily observed that the cell contents is much more highly differenti- ated than in the preceding group. The chlorophyll is deposited in plastids of definite form, although this color is often masked by a brown pigment which causes the characteristic appearance of these plants when associated in masses. The oil drops seen in the cells are the product of photosynthesis—starch not being formed. Some species, however, can live upon decaying or- ganic matter and in consequence contain colorless plastids. In the free swimming forms the motion consists of an irregular. 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 Curtis, Carlton Clarence, 1864-1945. New York, H. Holt
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisher, booksubjectbotany
