. Plant anatomy from the standpoint of the development and functions of the tissues, and handbook of micro-technic. 1, F) the number of chromosomes sent to each poleis 8, which is one-half the number in the ordinary vegetativedivisions. The reduction in the number of the chromosomeshere points to the archesporium as the homologue of the grand-mother cells of the microspores. Each daughter cell of thearchesporium divides once, yielding a row of four cells or mega-spores within the nucellus (Fig. 131, G). Only the uppermostmegaspore, m, proceeds to grow. As it elongates it crowds thethree disint
. Plant anatomy from the standpoint of the development and functions of the tissues, and handbook of micro-technic. 1, F) the number of chromosomes sent to each poleis 8, which is one-half the number in the ordinary vegetativedivisions. The reduction in the number of the chromosomeshere points to the archesporium as the homologue of the grand-mother cells of the microspores. Each daughter cell of thearchesporium divides once, yielding a row of four cells or mega-spores within the nucellus (Fig. 131, G). Only the uppermostmegaspore, m, proceeds to grow. As it elongates it crowds thethree disintegrating megaspores toward the micropylar end(Fig. 131, H) where they are soon lost sight of. Details in Division of Megaspore Grandmother Cell.—Thedetails in the division of the megaspore grandmother cell are es-sentially like those in the microspore grandmother cell, and weassume that here also in respect of a group of characters borneby a single chromosome two of the four megaspores descendedfrom the grandmother cell would be of paternal and two ofmaternal origin, as shown in I, Fig. 126. 228 REPRODUCTION. em 34 FIG. 131.—Stages in the formation of the megaspore, its germination, fertilization ofthe egg and endosperm nuclei, and germination of fertilized egg and endosperm cells. of ovule at o; B, nu, nucellus; Ca, nu, nucellus, a, archesporium; in, forwardgrowth of tissue to form the integument; Cb, nu, nucellus; in. integument; D, more highlymagnified drawing of o in A showing archesporial cell at a; E, a, archesporial cell enlargedand ready for division; nu, tissue of the nucellus; F, a, archesporial cell dividing, nu, nucellus;G, row of four megaspores descended from the archesporial cell, only the upper one, , the others soon to disintegrate; H, the megaspore, m, enlarging, the othersdisappearing; /, nucleus of the megaspore divided into two, md; J, continued nucleardivision has resulted in eight, namely, three antipodal nuclei, aw, at the up
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