. Botany; principles and problems. Botany. 102 BOTANY: PRINCIPLES AND PROBLEMS seed plants; and the herbaceous condition, where the stems are much softer and shorter-lived, has apparently been derived from it in response to climatic changes or for other reasons. In herbaceous species, the amount of fibro-vascular tissue has become proportionally very much less. This may be due simply to a decrease in the activity of the entire cambium, or to the breaking up of the cylinder into separate bundles, but in general. Fig. 53, Fig. 54. Fig. 53.âTransverse section of a one-year-old twig of the sweet g
. Botany; principles and problems. Botany. 102 BOTANY: PRINCIPLES AND PROBLEMS seed plants; and the herbaceous condition, where the stems are much softer and shorter-lived, has apparently been derived from it in response to climatic changes or for other reasons. In herbaceous species, the amount of fibro-vascular tissue has become proportionally very much less. This may be due simply to a decrease in the activity of the entire cambium, or to the breaking up of the cylinder into separate bundles, but in general. Fig. 53, Fig. 54. Fig. 53.âTransverse section of a one-year-old twig of the sweet gum {Liquid- amhar), showing the continuous fibro-vascular cylinder. Fig. 54.âTransverse section of a one-year-old twig of the sycamore (Platanus), showing the fibro-vascular cylinder broken up into segments by the development of wide rays. â {Figs. 53 and 54 from Sinnott and Bailey). any herbaceous stem is roughly comparable to a one-year-old twig of the particular woody stem-type from which it has been evolved. The herbaceous stem in Fig. 55, with its thin but continuous vascular ring, has probably arisen from some such woody form as is shown in Fig. 53, where the vascular ring is similarly continuous and homogeneous. The stem in Fig. 56, however, in which the cylinder has been broken into distinct and completely separate bundles, is quite different in type and has probably arisen from a woody stem somewhat resembling that in Fig. 54, where the vascular ring is divided into segments by the development of very wide rays. Cambial activity is usually weaker opposite these rays than opposite the woody segments of the cylinder, and in the stouter herbs of this type,. 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 Sinnott, Edmund Ware, 1888-. New York, McGraw-Hill
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectbotany, bookyear1923
