. Foundations of Botany. Botany. 100 FOUNDATIONS OF BOTANY a solid steel or iron rod of the same size would be too stiff for this use. 111. The Dicotyledonous Stem, thickened by Secondary Growth. — Cut off, as smoothly as possible, a small branch of hickory and one of white oak above and below each of the rings of scars already mentioned (Sect. 77), and count the P rings of wood above and below each ring of scars. How do the numbers correspond? What does Phi this indicate ? Count the rings of wood on the cut-off ends C of large billets of some of the following woods: locust, chestnut, syca- mo
. Foundations of Botany. Botany. 100 FOUNDATIONS OF BOTANY a solid steel or iron rod of the same size would be too stiff for this use. 111. The Dicotyledonous Stem, thickened by Secondary Growth. — Cut off, as smoothly as possible, a small branch of hickory and one of white oak above and below each of the rings of scars already mentioned (Sect. 77), and count the P rings of wood above and below each ring of scars. How do the numbers correspond? What does Phi this indicate ? Count the rings of wood on the cut-off ends C of large billets of some of the following woods: locust, chestnut, syca- more, oak, hickory. Do the successive rings of the same tree agree in thickness ? Why ? or why not ? Does the thickness of the rings appear uniform all the way round the stick of wood? If not, the rea- son in the case of an up- right stem (trunk) is per- haps that there was a greater spread of leaves on the side where the rings are thickest1 or because there was unequal pressure, caused by bending before the wind. Do the rings of any one kind of tree agree in thickness with those of all the other kinds ? What does this show ? In all the woods examined look for : (a) Contrasts in color between the heartwood and the 1 See Sect. 118. 2 This is admirably shown in locust and osage JR JR Fig. 71. —Cross-Section of a Three-Year-Old Linden Twig. (Much magnified.) P, epidermis and corky layer of the bark ; Phi, bast; C, cambium layer ; JR, annual rings of wood. red cedar, black walnut, barberry, black. 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 Bergen, Joseph Y. (Joseph Young), 1851-1917. Boston, Ginn & company
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