. Lectures on the evolution of plants. Botany; Plants. EVOLUTION OF PLANTS of the higher forms, such as the long cells in the stems of a good many flowering plants. Much more commonly the division of the nucleus is preceded by a number of complicated changes, result- ing in the breaking up of the linin-thread into separate pieces or segments (chro- mosomes) and a fur- ther splitting of these segments into halves. Two groups of segments are thus formed, which sep- arate and rearrange themselves to form the daughter-nuclei. This indirect division (Mitosis, Karyokine- sis) is the only form found
. Lectures on the evolution of plants. Botany; Plants. EVOLUTION OF PLANTS of the higher forms, such as the long cells in the stems of a good many flowering plants. Much more commonly the division of the nucleus is preceded by a number of complicated changes, result- ing in the breaking up of the linin-thread into separate pieces or segments (chro- mosomes) and a fur- ther splitting of these segments into halves. Two groups of segments are thus formed, which sep- arate and rearrange themselves to form the daughter-nuclei. This indirect division (Mitosis, Karyokine- sis) is the only form found in the actively dividing cells of the higher plants. Besides the nucleus there are found in most plant cells certain bodies known as "; (Fig. 1, B, pi.) These are similar to the cytoplasm in composition, and are very important in the nutrition of the cell. Among them are the green corpuscles — " chloroplastids " or chromatophores — in which are contained the green pigment, chlorophyll, which plays so important a role in the green plants. The red and. Fig. 3. Four cells from the growing tip of the root of an onion, showing different stages in the division of the cell-nucleus. In B the nuclear membrane has disap- peared and the nuclear segments or chro- mosomes (cr) are arranged in a plate at the equator of the nuclear spindle, which is composed of the "spindle-fibres," /. In C the two groups of chromosomes have moved to the poles of the nuclear spindle. In D the young division-wall, p, has been 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 Campbell, Douglas Houghton, 1859-1953. New York, The Macmillan Co. , London, Macmillan & Co. , Ltd.
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Keywords: ., bookcentury1800, bookdecade, booksubjectbotany, booksubjectplants
