. Adventures with animals and plants. Biology. All Food Is Made by Green Flants unit hi Fig. 178 (left) The smooth paperlike bark of the birch with its conspicuous leiiticels. Can yon name another tree ivhose young tivigs have con- spicuous lenticels? (Schneider and schwartz) Fin. 179 (below) Diagram of a young ivoody stem. How does this steTU differ from most root si' Wl:iat are the parts of the vascular c y Under? is never lost; the tree keeps a smooth bark throughout its Hfe. The vascular cylinder is much like the one in roots. It consists of phloem, cam- Epidermis bium, and xylem. But in t
. Adventures with animals and plants. Biology. All Food Is Made by Green Flants unit hi Fig. 178 (left) The smooth paperlike bark of the birch with its conspicuous leiiticels. Can yon name another tree ivhose young tivigs have con- spicuous lenticels? (Schneider and schwartz) Fin. 179 (below) Diagram of a young ivoody stem. How does this steTU differ from most root si' Wl:iat are the parts of the vascular c y Under? is never lost; the tree keeps a smooth bark throughout its Hfe. The vascular cylinder is much like the one in roots. It consists of phloem, cam- Epidermis bium, and xylem. But in the center there Cork is usualK' a fourth cylinder of thin- Cortex walled cells, the pith. Pith is very rarel\' found in roots but is found in most stems. Compare Figures 176 and 179. This vascular cylinder connects at its lower end with the vascular cylinder of the roots. At its upper end it branches Xylem many times and in each leaf branches again, forming the veins of the leaves. Cambium You will find it interesting to study a young stem as described in Exercise 8. How stems grow longer and branch. A Cortex swing fastened to one of the lower limbs of a tree remains the same distance from the ground \ear after year; yet the tree jrrows taller all the time. FA'idently the lower portion of the trunk docs not lengthen. In fact, the tree lengthens only near its tip. In parts of the world where there are distinct seasons growth ceases during the winter. At this time the cells at the tip of the stem arc covered by heavy scales, forming the tennincil Lentice. 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 Kroeber, Elsbeth, 1882-; Wolff, Walter Harold, 1901-. Boston : D. C. Heath
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