. Introduction to botany. Botany. 160 IXTEODUCTION TO BOTANY em<. starch, and oil are highly valuable for human food, and so is sugar, which occurs in small quantities in all the bread grains and in considerable amounts in the best varieties of sweet corn. The selection and cultivation of plants like the grains, which contain much digest- ible food in a concentrated form, and which may retaui their food value for some years with little loss, marked a long step upward m the civilization of the human race. 151. The seed coat. The seed coat is more or less efficient in protectmg its con- tents
. Introduction to botany. Botany. 160 IXTEODUCTION TO BOTANY em<. starch, and oil are highly valuable for human food, and so is sugar, which occurs in small quantities in all the bread grains and in considerable amounts in the best varieties of sweet corn. The selection and cultivation of plants like the grains, which contain much digest- ible food in a concentrated form, and which may retaui their food value for some years with little loss, marked a long step upward m the civilization of the human race. 151. The seed coat. The seed coat is more or less efficient in protectmg its con- tents from mechan- ical injury, such as crushing, and in many cases it pro- tects the more per- ishable materials within it from de- cay. Before germi- nation can begin, a certain amount of moisture must usually soak into the seed, either through the gen- eral surface, as in most seeds, or, in such hard-shelled seeds as the coco- nut, hickory nut, walnut, and but- ternut, through a thin or soft place in the wall. Usually the little opening in the ovule, known as the micnipyle (fig. 119, m), remains in the seed and servi's to admit moisture. The coats of many seeds liave wings or outgTOwths of hairs which aid in their dispersal. Other modifications in the coats. Fig. 143. Grain and seedling of corn ,1, lengthwise section of grain; B, the embryo re- moved; C, seedling; ph, endosperm; em, embryo; , sheath covering tip of rudimentary root; sc, scutellum, or absorbing cotyledon; pi, plumule; sh, sneath-like leaf in M-hich the first foliajje leaves are inclosed; ;-, iirst root, springiiii;- from witliin ; r'later-formed roots arising from other parts of the grain. 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 Bergen, Joseph Y. (Joseph Young), 1851-1917; Caldwell, Otis William, 1869- joint author. Boston, New Yo
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