. Agricultural botany, theoretical and practical. Botany, Economic; Botany. 272 REPRODUCTION chalaza and micropyle are all in the same straight line, as at r, Fig. 98 : such ovules are described as oi-thotropous. When the ovule during its development becomes inverted as at 2, Fig. 98, the micropyle lies close to the funicle : this form is met with in the majority of common flowering plants, and is spoken of as an anatropoiis ovule. Among cruciferous plants, and also among the Caryophyllacese and Cheno- podiaceae, the ovules are more or less kidney-shaped, the nucellus and integu- ments being c
. Agricultural botany, theoretical and practical. Botany, Economic; Botany. 272 REPRODUCTION chalaza and micropyle are all in the same straight line, as at r, Fig. 98 : such ovules are described as oi-thotropous. When the ovule during its development becomes inverted as at 2, Fig. 98, the micropyle lies close to the funicle : this form is met with in the majority of common flowering plants, and is spoken of as an anatropoiis ovule. Among cruciferous plants, and also among the Caryophyllacese and Cheno- podiaceae, the ovules are more or less kidney-shaped, the nucellus and integu- ments being curved or bent: ovules of this type are- described as campylotropous. At an early period in the development of the ovule a specially large cell termed the onbryo-sac makes its ap- pearance in the tissue of the nucellus at a point near the micropyle of the ovule. Within it a series of seven new cells are developed somewhat as follows. The primary nucleus of the embryo-sac first divides, and the two halves then travel to opposite ends of the cell. Here each of these two new nuclei divides into four, so that at this stage eight nuclei are present, each of which has a certain portion of cytoplasm associated with it. After this, one of the nuclei from the chalazal end and one from the micropylar end travel back to. 3 4 Fig. 98—I. External view of an orlhotro- pous ovule. 2. The same of an anatropoiis ovule. 3. Longitudinal section of i. 4. Longitudinal section of 2. / Funicle; m micropyle ; h chalaza ; c coats of ovule; n nucellus ; e 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 Percival, John, 1863-1949. New York, H. Holt
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