X CONTENTS 



PAGE 



21. Tissues . . . . ...... 22 



22. Method of study of functions and organs .... 23 



IV. THE ROOTS 



23. Functions of roots 24 



24. Roots hold the stem firmly in position .... 24 



25. Roots were first developed for fixation .... 26 



26. Shrinkage of roots to aid in fixation 27 



27. The structure of the root 28 



28. Climbing roots 28 



29. Stilt roots 29 



30. Columnar roots 29 



31. Keel or ballast roots 30 



32. Substances of which the soil is composed .... 30 



33. The soil and root-hairs adhere 31 



34. Root-hairs and the region from which they arise . . 31 



35. Action of roots which have been deprived of hairs . . 32 



36. Can water be taken through the leaves ? . . . .33 



37. The manner in which root-hairs take in liquids . . 34 



38. Action of sugar 35 



39. Another method of imitation of the action of root-hairs . 35 



40. Action of root-hairs on particles of mineral substance . 36 



41. The fate of the particles of soil 37 



42. Food-material in the soil, and how the plant finds it . 38 

 43. The tips of primary or main roots point downward . . 39 

 44. The tips of branches of the main roots are directed hori- 

 zontally .39 



45. Sensitiveness of the roots to moisture .... 40 



46. Roots bend away from light 41 



47. The tip of the root is protected by a sheathing cap . . 42 



48. The sensitiveness of roots to touch with solid objects . 43 



49. The roots of air-plants .44 



50. Parasitic roots 45 



51. Method of germination and growth of the dodder . 46 



52. Union of roots with fungi 47 



53. Roots as storage organs 48 



