. The botany of crop plants; a text and reference book. Botany, Economic. 96 BOTANY OF CROP PLANTS Embryo.—In the very young stage, prior to fertilization, the axis of the ovule is parallel with that of the ovary. Soon in its development, the ovule turns so that its micropyle is directed downward (Fig. 33). At first, the young ovule does not fill the ovary cavity, but soon does so by further growth. The ovule is attached along its side to the ovary. The groove indicates the position and extent of this at- tachment. The first pair of seminal (seed) rootlets appears in the embryo about four week
. The botany of crop plants; a text and reference book. Botany, Economic. 96 BOTANY OF CROP PLANTS Embryo.—In the very young stage, prior to fertilization, the axis of the ovule is parallel with that of the ovary. Soon in its development, the ovule turns so that its micropyle is directed downward (Fig. 33). At first, the young ovule does not fill the ovary cavity, but soon does so by further growth. The ovule is attached along its side to the ovary. The groove indicates the position and extent of this at- tachment. The first pair of seminal (seed) rootlets appears in the embryo about four weeks after poUination. About a week later, two other rootlets appear above the first pair, and Brenchley describes a fifth lateral rootlet, which does not appear until quite late. Endosperm.—In about a week or ten days after fertihzation, a definite tissue is formed within the embryo sac. This is the endosperm. About seven or eight days later, the aleurone layer is marked off, appearing first on the dorsal side. According to Brenchley, starch first begins to appear in the "flank" cells about the eleventh day after pollination. Eckerson points out that the actual time of the beginning of deposi- tion depends upon the relative activity of the leaves in making sugar and of the embryo in assimilating it. Infiltration of starch is complete in about five weeks after polHnation. It is held that reserve nitrogenous matter enters the endosperm at the same time as the starch. Grain Coats.—Before fertilization, the grain coats are as follows:. mi)\e Fig. 33.—Diagram- matic section of young ovary of wheat. {After Bessey.). 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 Robbins, Wilfred William, 1884-1952. Philadelphia, P. Blakiston's Son & Co
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Keywords: ., booka, bookcentury1900, bookdecade1910, booksubjectbotanyeconomic
