. Beginnings in agriculture. Agriculture. THE NATURE OF PLANTS 109 or pores for it to enter, as we might suppose. It must pass directly through the walls, or surfaces, of the cells. It is able to do this because the cell contains sap, which is a stronger hquid than the soil water. The sap therefore draws or sucks the soil water through the walls. As the hairs are slender and very numerous, they are in contact with a large area of soil and consequently take in much soil water. The surfaces of the rootlets themselves also take in some soil water. The root-hairs help to secure the plant-food in a
. Beginnings in agriculture. Agriculture. THE NATURE OF PLANTS 109 or pores for it to enter, as we might suppose. It must pass directly through the walls, or surfaces, of the cells. It is able to do this because the cell contains sap, which is a stronger hquid than the soil water. The sap therefore draws or sucks the soil water through the walls. As the hairs are slender and very numerous, they are in contact with a large area of soil and consequently take in much soil water. The surfaces of the rootlets themselves also take in some soil water. The root-hairs help to secure the plant-food in another way. They are provided with an acid, which, when it comes in contact with the soil particles, dissolves food elements that are needed. These are taken up by the soil water and so enter the plant. Once inside, the soil water, contain- ing its plant-food, passes into the root- lets, the roots, and up into the stem, by the same process by which it entered the root-hairs. It finally reaches the leaves, where, by the aid of sunshine, the water taken from the soil is united with the food taken from the air through the leaves, and starch, an im- portant plant-food, is formed. The plant mixes, or combines, several sub- stances to make its food, much as our mothers mix flour, milk, yeast, lard, and salt to make bread. Perhaps we shall now understand why the roots cannot use solid soil particles. There is no place for solid particles to enter the fine root-hairs. It may be said that roots drink their food rather than eat Fig. 51. - The root-hairs cling to the 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 Mann, Albert Russell, 1880-. New York, Macmillan company
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