A practical course in botany : with especial reference to its bearings on agriculture, economics, and sanitation . one? (77.) Experiment 53. To test the capacity of soils for absorbing andretaining moisture. — Arrange, as shown in Fig. 82, a number of long-necked bottles from which the bottom has been removed. This can bedone by making a small indentation with a file at the point desired andleading the break round the circumference with the end of a glowing wireor a red-hot poker. The crack will follow the heated object with sufficient Fig. 81.—Arrangement forestimating the force of root pres-
A practical course in botany : with especial reference to its bearings on agriculture, economics, and sanitation . one? (77.) Experiment 53. To test the capacity of soils for absorbing andretaining moisture. — Arrange, as shown in Fig. 82, a number of long-necked bottles from which the bottom has been removed. This can bedone by making a small indentation with a file at the point desired andleading the break round the circumference with the end of a glowing wireor a red-hot poker. The crack will follow the heated object with sufficient Fig. 81.—Arrangement forestimating the force of root pres-sure : s, stub of the cut stem ; g,glass tubing joined by means ofthe rubber tuijing, t, to the stem ;m, mercury forced up the glasstube by water, w, pumped fromthe soil by the roots. 68 PRACTICAL COURSE IN BOTANY regularity to answer the purpose. Tie a piece of thin cloth over the mouthof each bottle and invert with the necks extending an inch or two intoempty tum!)lers placed beneath. Fill all to the same height with soils ofdifferent kinds — sand, clay, gravel, loam, vegetable mold, etc. — and pour. Fig. 82. —Apparatus for testing the capacity of soils to take in and retainmoisture. over each the same quantity of water from above. Watch the rate atwhich the liquid filters through into the tumblers. Which loses its mois-ture soonest ? Which retains it longest ? Next leave the soils in the bottles dry, fill the tumblers up to the necksof the bottles, and watch the rate at which the water rises in the differentones. The power of soils to absorb moisture is called capillarity. Whichof your samples shows the highest capillarity ? Which the lowest ? Doyou observe any relation between the capillarity of a soil and its power ofretention ? 68. Roots as holdfasts. — One use of ordinary roots isto serve as props and stays for anchoring plants to the herbs and shrubs, and vegetation generally that isexposed to much stress of weather, are apt to have large,strong ro
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