CONTENTS xm 



VI. Stems 



PAGI! 



§ 119. The nature of stems 93 



§ 120. Stems are made up of sections or internodes ... 94 



§ 121. Branches arise at the nodes or joints only ... 94 



§ 122. Relation of the leaves and branches 94 



§ 123. Leaf traces 95 



§ 124. Relation of leaves and flowers 95 



§ 125. Structure of stems . - 95 



§ 126. Uses of stems 96 



§ 127. Methods by -which firmness is secured .... 97 



§ 128. Arrangement of dead cells to secure firmness of stems . 98 



§ 1"29. Arrangement of mechanical tissues in a stem of a grass 99 



§ 130. Mechanical tissues in a sunflovfer stem .... 100 



§ 131. Mechanical tissues in a carnation stem .... 100 



§ 132. Arrangement of mechanical tissues in a petiole . . 101 



§ 133. The firmness of plants that become limp when dried . 101 



§ 134. Stems as conducting organs 102 



§ 135. Upward path of sap 102 



§ 136. Path of sap in large trees 103 



§ 137. Girdling 103 



§ 138. Downward path of material from the leaf . . . 103 



§ 139. Forces which carry the sap upward through the stem . 104 



§ 140. Root, or bleeding pressure 105 



§ 141. The flow of sap of the sugar maple 105 



§142. Dew 106 



§ 143. How to cause a plant to form dew at any time . . 106 



§ 144. Lifting power of leaves and branches .... 107 



§ 145. Growth of stems 108 



§ 146. Action of embryonic tissue of a tree .... 108 



§ 147. Growth in length and diameter 109 



§ 148. Measurement of growth in length 109 



§ 149. Measurement of growth in diameter .... 109 



§150. The bark 110 



§ 151. Growth of a corn stem Ill 



§ 152. Nodding or circular movements due to unequal growth . 112 



§ 153. Length of life 112 



