Students' handbook to accompany Plants and their uses . FIG. 46. Formation ofknots due to figure gives part ofa lengthwise section ofa stick of birch wood a, section of the base ofa branch which persisteduntil the tree was felled ; b, section of the base of abranch which died someyears earlier and is nowcovered by several layers of younger wood 68 INT in (DICTION TO BOTANY. As the brandi lengthens, it somewhat displaces the annuallayers of the stem from which it grows, and the branch formsits own animal rings. Knots arc not all due to the growthof brandies, but most of them are, a
Students' handbook to accompany Plants and their uses . FIG. 46. Formation ofknots due to figure gives part ofa lengthwise section ofa stick of birch wood a, section of the base ofa branch which persisteduntil the tree was felled ; b, section of the base of abranch which died someyears earlier and is nowcovered by several layers of younger wood 68 INT in (DICTION TO BOTANY. As the brandi lengthens, it somewhat displaces the annuallayers of the stem from which it grows, and the branch formsits own animal rings. Knots arc not all due to the growthof brandies, but most of them are, as may be seen fromfigure 40. If a knot-forming branch dies early, new woodforms over it and covers it np, as the lignre shows; but if itcontinues to live as long as the- main stem does, it gives rise to a knot that reaches to the outer- H most layer of wood in the stem. In figure 40 which knot, a or b,would be the more likely to in-jure the timber? 66. Internal structure of the mon-ocotyledonous stem. In the veryyoung monocotyledonons stems ofseedlings thefibrovasenlar bundlesare constructed like those of di-cotyledons. The wood elementsare on the one side and the corti-cal elements on the other. In thefull-orown stems of most mono- O cotyledons the bundles have theirvessels and other wood elements arranged in a hollow cylinderinclosing that part of the bundle which corresponds
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Keywords: ., bookcentury1900, bookcollection, bookdecade191, booksubjectbotany
