. Carnegie Institution of Washington publication. . Flo. 46.—Ovuie of N. odo- FIG. 47.—Embryo sac of N. mlirrata; longitudinal section of ovule at time of rata, from a half-grown bud, flowering. From a photomicrograph, showing archesporium. From a photomicrograph. projects into the enlarging ovary cell. This swells at the end into a knob, an integument of two cell-layers grows up around the knob, and then a second integument outside the first. When the inner integument has reached the height of the nucellus, the outer one is about half as high (cf. Fig. 46). Meanwhile the knob has turned over
. Carnegie Institution of Washington publication. . Flo. 46.—Ovuie of N. odo- FIG. 47.—Embryo sac of N. mlirrata; longitudinal section of ovule at time of rata, from a half-grown bud, flowering. From a photomicrograph, showing archesporium. From a photomicrograph. projects into the enlarging ovary cell. This swells at the end into a knob, an integument of two cell-layers grows up around the knob, and then a second integument outside the first. When the inner integument has reached the height of the nucellus, the outer one is about half as high (cf. Fig. 46). Meanwhile the knob has turned over at right angles to the supporting column in its change toward anatropy. A large archesporial cell is now visible at the apex of the nucellus, covered by a layer of cells. The archesporial cell presents five times as large a surface in longitudinal sec- tion as the surrounding cells ; its nucleus is as large as an entire cell of the nucellus, is rather poor in contents, and has a single dense nucleolus. Its further development has been described for N. odorata by Cook (1902). According to his account, a tapetal cell is cut off at the outer end of the archesporial cell (cf. Fig. 46), and from the former several tapetal cells arise by a variable series of divisions. Three potential megaspores are next cut off from the mother-cell. These rapidly degenerate, leaving a. 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 Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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