. Foundations of Botany. Botany. 244 FOUNDATIONS OF BOTANY however, to retard the occurrence of conjugation by leaving the Spirogyra filaments in very cold water over night, and in this way the successive steps of the conjugating process may be studied by daylight. In such ways the series of phenomena shown in Fig. 178, II, has been accurately followed. If the student cannot follow these operations under the microscope, he may, at least, by looking over the yellower portions of a mass of Spirogyra find threads con- taining fully formed zygospores, like those shown in B, Fig. 178. THE STUDY OF
. Foundations of Botany. Botany. 244 FOUNDATIONS OF BOTANY however, to retard the occurrence of conjugation by leaving the Spirogyra filaments in very cold water over night, and in this way the successive steps of the conjugating process may be studied by daylight. In such ways the series of phenomena shown in Fig. 178, II, has been accurately followed. If the student cannot follow these operations under the microscope, he may, at least, by looking over the yellower portions of a mass of Spirogyra find threads con- taining fully formed zygospores, like those shown in B, Fig. 178. THE STUDY OF PLEUROCOCCUS 277. Occurrence.—Pleurococcus may be found on old fences, roofs, and many similar places, particularly on the bark of the north side of trees. The individual plants cannot be detected by the naked eye, but when grouped in masses they form a powdery green covering over indefinite areas of bark. Plenty are seen where it is moist. 278. Microscopical Examination of Pleurococcus. — Scrape a minute quantity of Pleurococcus from a specimen on bark, place it in a drop of water on a slide, distributing it slightly in the water, lay on it a cover-glass and ex- amine with a power of 200 or more diameters. Sketch with the cam- era lucida one of the largest cells, some of intermediate size, and one of the smallest, beside several divisions of the stage microm- eter. Note the clearly de- fined cell-wall of cel- lulose, enclosing the protoplasmic contents, usually green through- out. Do any cells show a nucleus like that in Fig. 179, A ? Test the cells with iodine solution for 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 Bergen, Joseph Y. (Joseph Young), 1851-1917. Boston, Ginn & company
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