. Botany; principles and problems. Botany. 274 BOTANY: PRINCIPLES AND PROBLEMS small branch near by is cut off a cell which develops into an antheridium. One of the sperms here developed enters the oogonium and fertilizes the egg, producing a heavy-walled oospore. 4. Conjugales, the Pond Scums, Desmids, and Diatoms.—The plant body of these algae is a single cell or an unbranched fila- ment. The species are all confined to fresh water and are dis-. FiG. 153.—Spirogyra. Two adjacent filaments, showing stages in sexual reproduction. Cell a shows the normal, resting condition, with the spirally pl
. Botany; principles and problems. Botany. 274 BOTANY: PRINCIPLES AND PROBLEMS small branch near by is cut off a cell which develops into an antheridium. One of the sperms here developed enters the oogonium and fertilizes the egg, producing a heavy-walled oospore. 4. Conjugales, the Pond Scums, Desmids, and Diatoms.—The plant body of these algae is a single cell or an unbranched fila- ment. The species are all confined to fresh water and are dis-. FiG. 153.—Spirogyra. Two adjacent filaments, showing stages in sexual reproduction. Cell a shows the normal, resting condition, with the spirally placed, band-like chromatophore, in which numerous circular pyrenoids can be seen. Cells b and c are sending out conjugating tubes to each other. The con- tents of cells d and e have contracted somewhat and the contents of e is passing over through the conjugating tube and uniting with d. At/is shown the mature zygospore which has arisen from the union of two cells. X 150. tinguished from other Chlorophyceae by the absence of zoospores or other means of asexual reproduction, the absence of motile cells of any sort, the occurrence of large and conspicuous chloro- plastids, and the characteristic manner in which sexual reproduc- tion is brought 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 Sinnott, Edmund Ware, 1888-. New York, McGraw-Hill
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectbotany, bookyear1923
