. The life of the plant. Plant physiology. GROWTH 211 this alternation of dark and light layers in every splinter, even in a match. The microscope betrays the immediate reason for this difference. This figure (fig. 62) shows a small piece of pine wood, the transverse section of a match. Across the middle of it runs the boundary between two annual layers.^ In the lower part lie some summer and all the autumn cells, say of last year ; in the upper the spring cells of the present. Fig. 62. year. The sharp transition from the autumn to the spring cells is easily perceived : the former have a flat
. The life of the plant. Plant physiology. GROWTH 211 this alternation of dark and light layers in every splinter, even in a match. The microscope betrays the immediate reason for this difference. This figure (fig. 62) shows a small piece of pine wood, the transverse section of a match. Across the middle of it runs the boundary between two annual layers.^ In the lower part lie some summer and all the autumn cells, say of last year ; in the upper the spring cells of the present. Fig. 62. year. The sharp transition from the autumn to the spring cells is easily perceived : the former have a flat shape, thick walls, small and narrow cavities ; the others are almost square, have thin walls and large cavities. For a long time botanists could not account for this change in the form of the cells laid down at different seasons of the year, until they conceived the idea that the fact must depend on the mutual pres- sure, the mutual tension of the tissues. We made 1 The transverse line dividing the section into two parts—to the right and to the left—is the medullary ray (see previous chapter).. 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 Timiri?a?zev, K. A. (Kliment Arkad?evich), 1843-1920; Sheremeteva, Anna, tr. London, New York, Bombay, Calcutta, Longmans, Green, and Co.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectplantph, bookyear1912
