. Foundations of Botany. Botany. 242 FOUNDATIONS OF BOTANY diameters, then with a power of 200 diameters or more. Note the structure of the filaments. Of what is each made up? Compare with the structure of Oscillatoria. Move the slide so as to trace the whole length of several filaments, and, if the unbroken end of one can be found, study and sketch it. Study with the higher power a single cell of one of the larger filaments and ascertain the details of structure. Try to discover, by focusing, the exact shape of the cell. How do you know that the cells are not flat? Count the bands of chloroph
. Foundations of Botany. Botany. 242 FOUNDATIONS OF BOTANY diameters, then with a power of 200 diameters or more. Note the structure of the filaments. Of what is each made up? Compare with the structure of Oscillatoria. Move the slide so as to trace the whole length of several filaments, and, if the unbroken end of one can be found, study and sketch it. Study with the higher power a single cell of one of the larger filaments and ascertain the details of structure. Try to discover, by focusing, the exact shape of the cell. How do you know that the cells are not flat? Count the bands of chlorophyll. The number of bands is an important characteristic in dis- tinguishing one species from another. Run in five-per-cent salt solution at one edge of the cover-glass (withdraw- ing water from the other edge with a bit of blotting paper). If any change in the appearance of the cell becomes evident, make a sketch to show it. What has happened to the cell-con- tents? Explain the cause of the change by reference to what you know of osmose. On a freshly mounted slide run under the cover-glass iodine solution, a little at a time, and note its action on the nucleus. Is any starch shown to be present? If so, just how is it distributed through the cell? 276. Reproduction of Spirogyra.— The reproductive process in Spirogyra is of two kinds, the simplest being a process of fission, or cell- division. The nucleus undergoes a very complicated series of transformations, which result in the division of the protoplasmic contents of a cell into two independent portions, each of which is at length surrounded by a complete cell-wall of its own. In Fig. 176. Fig. 177. —Process of Cell-Multi- plication in a Species of Pond- Scum. (Considerably magnified.) A, portion of a filament partly separated at a and completely so at b; B, separation nearly completed, a new partition of cellulose formed at a; C, another portion more magni- fied, showing mucous covering d, general cell-wall c, and a delic
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