CONTENTS xi 



54. Method of growth of roots 49 



55. Absorbing and fixing organs of the lower plants . . 50 

 56. Absorbing and fixing organs of the ferns, mosses, and 



liverworts ......... 50 



57. Method of fixation of the moulds and mushrooms . . 51 



V. THE LEAVES 



58. Absorption and fixation by the algae and bacteria . . 52 



59. Structure of leaves ........ 54 



60. Leaves with both surfaces alike ...... 56 



61. Compound leaves ........ 56 



62. Composition of the air ....... 57 



63. Gases of use to the plant ....... 57 



64. Functions of the leaf ........ 58 



65. The colors of leaves ........ 58 



66. Hidden chlorophyl ........ 59 



67. Characteristics of chlorophyl ...... 60 



68. Spectrum of chlorophyl ....... 60 



69. The leaf is a machine or mill ...... 61 



70. Quality of light most useful to the plant .... 61 



71. Light destroys chlorophyl ....... 62 



72. Light is necessary for the formation of chlorophyl in most 



instances .......... 62 



73. Capacity of leaves for the absorption of light ... 63 



74. Formation of food in chlorophyl-bearing organs . . 64 



75. Non-green colors ......... 65 



76. Origin of red colors ........ 65 



77. Changes in color ......... 66 



78. Autumnal colors ......... 67 



79. Uses of autumnal colors ....... 68 



80. Uses of red and other colors in flowers and fruits . . 68 



81. Characteristics of red and blue colors .... 69 



82. Red color as a shield ........ 69 



83. Red color as a heat producer . ... 69 



84. Red color as a heat saver ... ... 70 



85. Hairs as a protection to a leaf ...... 71 



