68 PRACTICAL COURSE IN BOTANY 
regularity to answer the purpose. Tie a piece of thin cloth over the mouth 
of each bottle and invert with the necks extending an inch or two into 
empty tumblers placed beneath. Fill all to the same height with soils of 
different kinds — sand, clay, gravel, loam, vegetable mold, ete. — and pour 
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Fic. 82. — Apparatus for testing the capacity of soils to take in and retain 
moisture. 
AC 
over each the same quantity of water from above. Watch the rate at 
which 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 necks 
of the bottles, and watch the rate at which the water rises in the different 
ones. The power of soils to absorb moisture is called capillarity. Which 
of your samples shows the highest capillarity? Which the lowest? Do 
you observe any relation between the capillarity of a soil and its power of 
retention? 
68. Roots as holdfasts. — One use of ordinary roots is 
to serve as props and stays for anchoring plants to the soil. 
Tall herbs and shrubs, and vegetation generally that is 
exposed to much stress of weather, are apt to have large, 
strong roots. Even plants of the same species will develop 
systems of very different strength according as they grow 
in sheltered or exposed places. 
