. Studies on the plant cell. Plant cells and tissues. No. 460.] STUDIES ON PLANT CELL.— V. 231 The fibrillae organize a multipolar spindle which is very vari- able in form, sometimes with broad poles of a multipolar diarch (Fig- 17) d) and at other times almost as pointed as in a typical bipolar spindle (Fig. 17, e). There are, of course, no centro- somes and the entire spindle in essentially of intranuclear origin. The history of its development recalls Miss Williams' account of the spindle in the pollen mother-cell of Passiflora (Sec. Ill, Amer. Nat., vol. 38, p. 738, 1904). During s


. Studies on the plant cell. Plant cells and tissues. No. 460.] STUDIES ON PLANT CELL.— V. 231 The fibrillae organize a multipolar spindle which is very vari- able in form, sometimes with broad poles of a multipolar diarch (Fig- 17) d) and at other times almost as pointed as in a typical bipolar spindle (Fig. 17, e). There are, of course, no centro- somes and the entire spindle in essentially of intranuclear origin. The history of its development recalls Miss Williams' account of the spindle in the pollen mother-cell of Passiflora (Sec. Ill, Amer. Nat., vol. 38, p. 738, 1904). During spindle formation the spirems of the sperm and egg nuclei can be readily distin- guished as was described by Blackinan ('98) and Chamberlain. Fig. 17. — Fertilization in/*(««j j^(>^*«. a, conjugating gamete nuclei; b, the gamete nuclei still separated, with nuclear membranes distinct, the maternal and paternal chromatin in two spirems; c, the nuclear membranes have disappeared and the two spirems lie close together surrounded by the fibrillse which will organize the first segmentation spindle;, <f, prophase of the first segmentation spindle, of the multipolar diarch type, paternal and maternal spirems still distinct; e, metaphase of first segmentation mitosis, maternal and paternal chromosomes now indistinguishable, beginning to split in the middle region (after Ferguson, :o4). ('99), but after the two sets of chromosomes are formed (twelve of each) the latter are brought so closely together at metaphase of mitosis that the paternal and maternal cannot be separated. All of the chromosomes are exactly alike and there is nothing in the form or size to distinguish one from another as certain. 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 Davis, Bradley Moore, 1871-. [Boston, Ginn and Co.


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