. Botany for agricultural students . Botany. SEEDLINGS OF THE GRASS TYPE 105 in connection with it, there is a principle which is reckoned with in growing certain plants of the Grass type. According to the depth of planting this temporary stem region is long or short. (Fig. 97.) This is due to the fact that the first node and, consequently, the first of the permanent roots are always estab- lished about the same distance under the surface of the soil, re- gardless of the depth at which the seed was planted. Therefore,. Fig. 99. — Stages in the development of the Onion seedling. A, section thro
. Botany for agricultural students . Botany. SEEDLINGS OF THE GRASS TYPE 105 in connection with it, there is a principle which is reckoned with in growing certain plants of the Grass type. According to the depth of planting this temporary stem region is long or short. (Fig. 97.) This is due to the fact that the first node and, consequently, the first of the permanent roots are always estab- lished about the same distance under the surface of the soil, re- gardless of the depth at which the seed was planted. Therefore,. Fig. 99. — Stages in the development of the Onion seedling. A, section through an Onion seed showing endosperm (en) and embryo (e) with the hypocotyl Qi) and cotyledon (c) indicated. B, seed germinating; g, ground line; s, seed; c, cotyledon; h, hj^ocotyl; r, radicle. C, seedling more de- veloped; c, cotyledon which is being pulled out of the seed; h, hypocotyl; I-, radicle; /, first leaf. D, a later stage of the seedling with cotyledon free from the seed and permanent root system (p) developing. a deep permanent root system, which is often desirable in order that the plant may withstand drought, is not secured by deep planting — a fact which has been well demonstrated in case of Corn and the small grains. Moreover, if the seed is planted too deeply, its food and energy may be exhausted before the plumule reaches the light, in which case the seedling is unable to continue its development. However, after the permanent roots are estabUshed they may. 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 Martin, John N. (John Nathan), b. 1875. New York : John Wiley & Sons, Inc.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
