Students' handbook to accompany Plants and their uses . ot tip is covered with severallayers of dead or dying cells, which makeup the rootci/i. As the root pushes its way111 rough the soil the rootcap is constantlybeing worn away on the outside. Duringthe seasons of activity the rootcap is con-tinually being rebuilt by the formation ofnew layers of cells on its inner older roots the epidermis has givenplace to barh\ which is composed of sev-eral layers of cells. If a cross section ofa very young root of a dicotyledonousplant is examined with a moderate mag-nification, it will be see
Students' handbook to accompany Plants and their uses . ot tip is covered with severallayers of dead or dying cells, which makeup the rootci/i. As the root pushes its way111 rough the soil the rootcap is constantlybeing worn away on the outside. Duringthe seasons of activity the rootcap is con-tinually being rebuilt by the formation ofnew layers of cells on its inner older roots the epidermis has givenplace to barh\ which is composed of sev-eral layers of cells. If a cross section ofa very young root of a dicotyledonousplant is examined with a moderate mag-nification, it will be seen that the cortexis made up of rather loosely aggregatedcells, while the central cylinder is moreclosely compacted. In the cylinder are 1(»ind a definite number of radially arranged tibrovascularbundles. Tin- woody strands of these bundles alternate withstrands of \\hat are kiio\ as />,t*f ///-,•/•*. shown in figure 44. 17. The root-hair cell. The general tubular structure ofroot hairs was very brietly rxplained in section 8. A root hair, 20. !•>. i Irosa -••! ii i cit i-i-nl nil portion of root of sweet ( . I -H/-//.S) •, : 0, mitrnnostla\ T of cells of cent nil c\ ; o, vessels ..I\ Hi-ions sizes; l»c ROOTS AND THEIK KELATIOiV TO PLANTS together with the minute sub-division of the epidermis fromwhich it springs (fig. 16, e), furnishes a good example of onekind of plant Each live root hair consists of an ex-tremely thin sac, the cell wall (shown in figs, 6 and 16merely as a continuous line bounding the root hairs), and theliving contents of the cell, known as the jn-»t»i>laxt. The cellwall consists of a material known as cclliilnxe, familiar to allin the microscopicfibers of cotton. Thecell contents, or pro-toplast, of a root hairconsists largely ofa nearly transparentportion, the cytoplasm,composed of nitroge-nous material whichmay be roughly com-pared to very thinwhite of egg. Within
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Keywords: ., bookcentury1900, bookcollection, bookdecade191, booksubjectbotany
