. Botany of the living plant. Botany; Plants. phl"\ V --^ Fig. 67. Diagram A shows arrangement of tissues in a young root of a Dicotyledon before cambial activity begins. B. the same when cambium can be clearly recognised. C. after secondary thickening has progressed. c=cortex, present in A and B, but in C it has been thrown off. phloem. />/;/"=secondary phloem. xylem. .vy"=secondary xylem. £.wr=primary medullary ray. mr" =secondary medullary ray. ;/i=pith. Compare Fig. 37, p. 58. the ground, while evi
. Botany of the living plant. Botany; Plants. phl"\ V --^ Fig. 67. Diagram A shows arrangement of tissues in a young root of a Dicotyledon before cambial activity begins. B. the same when cambium can be clearly recognised. C. after secondary thickening has progressed. c=cortex, present in A and B, but in C it has been thrown off. phloem. />/;/"=secondary phloem. xylem. .vy"=secondary xylem. £.wr=primary medullary ray. mr" =secondary medullary ray. ;/i=pith. Compare Fig. 37, p. 58. the ground, while evidence of the shrinkage is seen in transverse wrinkles on its surface. In most woody Dicotyledons the bulky cortex itself collapses and finally peels off. This is due to the formation of a band of cork, which originates from the pericycle, and cuts off the outer-lying tissues from physiological connection with those within, so that they perish (Fig. 67, C). Since the cortex makes up a very large proportion of the whole bulk of the root, the consequence in such cases is that at first the root appears to become thinner as it grows older. But as a matter of fact the central stele has meanwhile been increasing in bulk, and it is protected externally by the band of cork which originates from the pericycle. Since this cork may be further. 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 Bower, F. O. (Frederick Orpen), 1855-1948; Wardlaw, C. W. (Claude Wilson), 1901-. London, Macmillan and Co. , ltd.
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