. Botany, an elementary text for schools. Botany. 66 FOOD FEOM THE SOIL tions; and they are the principal means by which plant- food is absorbed from the soil, although the surfaces of the rootlets themselves do their part. Water-plants do not need an abundant system of root-hairs, and such plants depend largely on their rootlets. 139. OSMOSIS.—In order to understand how the water enters the root-hair, it is necessary that we study the physical process known as os- mosis. A salt solution sepa- rated hy a membrane from ivater absorbs some of the tvater and increases its otvn volume. First disso
. Botany, an elementary text for schools. Botany. 66 FOOD FEOM THE SOIL tions; and they are the principal means by which plant- food is absorbed from the soil, although the surfaces of the rootlets themselves do their part. Water-plants do not need an abundant system of root-hairs, and such plants depend largely on their rootlets. 139. OSMOSIS.—In order to understand how the water enters the root-hair, it is necessary that we study the physical process known as os- mosis. A salt solution sepa- rated hy a membrane from ivater absorbs some of the tvater and increases its otvn volume. First dissolve one ounce of saltpeter, which we may use as a fertilizer solution, in one pint of water, calling this so- lution No. I. For use in ex- periments later on, also dis- solve a piece of saltpeter not larger than a peach pit (about one-seventh ounce) in about one gallon of water, calling this solution No. II. Now fill the tube, C in Fig. 106, almost full of the strong solution I, and tie a piece of animal membrane (hog's bladder is excellent for this purpose) over the large mouth. A small funnel, with a long stem, may be used if one cannot obtain a tube like C. Then sink the tube, bladder-part down- wards, into a large bottle, A, of water until the level of liquid in the tube stands at the same height as that in the bottle. The tube may be readily secured in this position by passing it through a hole in the cork of the bottle. In a short time, we notice that the liquid in N begins to rise, and in an hour or so it stands as at F, say. This is an important result. The facts are that the liquids tend to diffuse, but the strong solution in N cannot pass. 105. Cross section of root, enlarged, showing 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 Bailey, L. H. (Liberty Hyde), 1858-1954. New York Ma
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