. Elementary botany. Botany. 362 RELATION TO ENVIRONMENT. apical cell, the root cap being cut off by successive divisions of the outer face, while the primary root tissues are deri\-ed from the three lateral Fig. 420. Median longitudinal section of the apex of a root of the barley, Hordeum vulgare. fe, calyptrogen; </, dermat- ogen; c, its thickened wall; pr, peri- blem; pi, plcrome; C7t, endodennis; i, intercellular air-space in process of formation; a, cell row destined to fonn a vessel; r, exfoliated cells of the root cap. (After Strasburger.) Fig. 421. Cross-section of fibrovasc
. Elementary botany. Botany. 362 RELATION TO ENVIRONMENT. apical cell, the root cap being cut off by successive divisions of the outer face, while the primary root tissues are deri\-ed from the three lateral Fig. 420. Median longitudinal section of the apex of a root of the barley, Hordeum vulgare. fe, calyptrogen; </, dermat- ogen; c, its thickened wall; pr, peri- blem; pi, plcrome; C7t, endodennis; i, intercellular air-space in process of formation; a, cell row destined to fonn a vessel; r, exfoliated cells of the root cap. (After Strasburger.) Fig. 421. Cross-section of fibrovascular bundle in adventitious root of Ranunculus re- pens. It', pcricycle; 5, four radial plates of xylem; alternating with them are groups of phloem. This is a radial bundle. (After De Bary.) Function of the root cap.—The root cap serves an important function in protecting the delicate mcristem or cambium at the tip of the root. These cells are, of course, very thin-walled, and while there is not so much danger that they would be injured from dr)'ness, since the soil is usually moist enough to prevent evaporation, they would be liable to injur)' from friction with the rough particles of soil. No similar cap is developed on the end of the stem, but the meristem here is protected by the overlapping bud- scales. One of the most striking illustrations of a root cap may be seen in the case of the Pandanus, or screw-pine, often grown in conservatories (see fig. 447). On the prop roots which ha\-e not yet reached the ground the root cap?; can readily be seen, since they are so large that they fit over the end of the root like a thimble on 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 Atkinson, George Francis, 1854-1918. New York : H. Holt
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