. Foundations of botany. ned ^^qsTYYTTYi^™™^ (Sect. 77), and count the rings of wood above andbelow each ring of scars. How do the numberscorrespond? What doesPhi this indicate ? Count the rings ofwood on the cut-off endsof large billets of someof the following woods:locust, chestnut, syca-more, oak, hickory. Do the successive ringsof the same tree agree inthickness ? Why ? or why not ?Does the thickness ofthe rings appear uniformall the way round the stickof 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 wher
. Foundations of botany. ned ^^qsTYYTTYi^™™^ (Sect. 77), and count the rings of wood above andbelow each ring of scars. How do the numberscorrespond? What doesPhi this indicate ? Count the rings ofwood on the cut-off endsof large billets of someof the following woods:locust, chestnut, syca-more, oak, hickory. Do the successive ringsof the same tree agree inthickness ? Why ? or why not ?Does the thickness ofthe rings appear uniformall the way round the stickof 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 therings are thickest ^ or because there was unequal pressure, caused bybending before the wind. Do the rings of any one kind of tree agree in thickness withthose 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 sapwood.^ 1 See Sect. 118. 2 This is admirably shown in red cedar, black walnut, barberry, blacklocust and osage JR Fig. 71. — Cross-Section of a Three-Year-OldLinden Twig. (Much magnified.) P, epidermis and corky layer of the bark ; Phi, bast;C, cambium layer ; JH, annual rings of wood. STRUCTURE OE THE STEM 101 (5) The narrow lines running in very young stems pretty straightfrom pith to bark, in older wood extending only a little of the wayfrom center to bark, the medullary rays, shown in Fig. (c) The wedge-shaped masses of wood between these. (d) The pores which are so grouped as to mark the divisionsbetween successive rings. These pores indicate the cross-sections of vessels or ducts. Xote the dis-tribution of the vessels in ~^-^. hN_^ x^T rings to which they belong, com-
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectplants, bookyear1901
