. Fundamentals of botany. Botany. SEED-BEARING PLANTS 421 373. Female Gametophyte.—During the first season the megaspore (Fig. 311) enlarges somewhat, and its nucleus divides several times, forming free nuclei. In this condi- tion it remains until the next season, when the formation of the gametophyte is carried to completion. As the gametophyte develops it feeds on the nuceUus, which is entirely consumed except for a thin membrane, which. Fig. 311.—White pine {Pinus Strobus). At left, megasporangimn with megaspore in the center; above, pollen grains in the micropyle and pollen chamber. At rig
. Fundamentals of botany. Botany. SEED-BEARING PLANTS 421 373. Female Gametophyte.—During the first season the megaspore (Fig. 311) enlarges somewhat, and its nucleus divides several times, forming free nuclei. In this condi- tion it remains until the next season, when the formation of the gametophyte is carried to completion. As the gametophyte develops it feeds on the nuceUus, which is entirely consumed except for a thin membrane, which. Fig. 311.—White pine {Pinus Strobus). At left, megasporangimn with megaspore in the center; above, pollen grains in the micropyle and pollen chamber. At right, pollen grains beginning to germinate; the cells of the integument have enlarged and closed the micropyle. (After Margaret C. Ferguson.) adheres to the surface of the gametophyte or endosperm, and a cap of tissue at the-tip of the gametophyte (Figs. 309, K, and 312).^ The archegonia, two to five in number, at the micropylar end of the gametophyte, are mature by the last of May or forepart of June, in the northern states. In Pinus the neck of the archegonium is very much re- ' In the seeds of some of the higher plants the tissue of the nucellus becomes filled with nourishment stored for the use of the developing embryo, during germination. It is then called 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 Gager, C. Stuart (Charles Stuart), 1872-1943. Philadelphia, P. Blakiston's son & co.
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Keywords: ., bookauthorgag, bookcentury1900, bookdecade1910, booksubjectbotany
