h of rotation 233

XXV.--FARM DRAINAGE 235
How surplus water affects fertility 235
Indications of a need of drainage 235
Drains:
Surface drains
Open ditch drains
Covered drains or under drains 236
Influence of covered drains on fertility 237
Location of drains:
Grade
Tile drains 238

GLOSSARY 241

LIST OF ILLUSTRATIONS

The farm equipment--plants, soils, animals, tools,
buildings _Frontispiece_

Figure Facing Page

1. Specimen plants for study 6

2. The first effort of a sprouting seed 7

3. Germinating seeds with roots 7

4. To show that plant roots take water from the soil 10

5. To show that plant roots take food from the soil 10

6. A radish root, from which the stored food has been
used to help produce a crop of seeds 11

7. A sweet-potato root producing new plants 11

8. Sweet-potato roots 14

9. Soy-bean roots 15

10. A plow stopped in the furrow, to show what it does to
the roots of plants when used for after-cultivation 18

11. A corn-plant ten days after planting the seed 19

12. To show where growth in length of the root takes place 22

13. Radish seeds sprouted on dark cloth 22

14. To show how water gets into the roots of plants 23

15. To show osmose 23

16. To show that roots need air 26

17. Comparison of fresh and boiled water 26

18. Comparison of moist sand and puddled clay 27

19. Comparing soils 32

20. Water-test of soils 33

21. To show what becomes of the water taken from the soil
by roots 40