. Elements of botany. Plants. LIVING PARTS OF THE STEM. 69 through which the ink has traveled. Repeat with several potatoes, cut crosswise through the middle. For the sake of comparison between roots and stems, treat any convenient root, such as a parsnip, in the same way. Examine longitudinal sections of some of the twigs, the potatoes, and the roots. In drawing conclusions about the channels through which the ink has risen (wiiich are those through which the crude sap most readily travels), bear in mind the fact that a slow soakage of the red ink will take place in all directions, and theref
. Elements of botany. Plants. LIVING PARTS OF THE STEM. 69 through which the ink has traveled. Repeat with several potatoes, cut crosswise through the middle. For the sake of comparison between roots and stems, treat any convenient root, such as a parsnip, in the same way. Examine longitudinal sections of some of the twigs, the potatoes, and the roots. In drawing conclusions about the channels through which the ink has risen (wiiich are those through which the crude sap most readily travels), bear in mind the fact that a slow soakage of the red ink will take place in all directions, and therefore pay attention only to the strongly colored spots or lines. What conclusions can be drawn from this experiment as to the course followed by the sap ? From the familiar facts that ordinary forest trees appar- ently flourish as well after the almost complete decay and removal of their heartwood, and that many kinds will live and grow for a considerable time after a ring of bark extend- ing all round the trunk has been removed, it may readily be inferred that the crude sap in trees must rise through some portion of the newer layers of the wood. Most dicotyledonous stems, when stripped of a ring of bark and then stood in water, as shown in Fig. 55, develop roots only at or near the upper edge of the stripped portion,^ and this would seem to prove that such stems send their building-material — the elab- orated sap — largely at any rate down through the bark. Its course is undoubtedly for the most part through the sieve-cells (Figs. 42- 45), which are admirably adapted to convey liquids. In addi. tion to these general upward and downward movements of 1 Tliis may be made the subject of a protracted class-room experiment. Strong shoots of willow should be used for the Fig. 55.— A Cutting Girdled and sending down Roots from the Upper Edge of the Girdled Please note that these images are extracted from scanned page images that may have been digitally enhanced fo
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectplants, bookyear1896
