CONTENTS xiii 



VI. STEMS 



PAGE 



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 



129. Arrangement of mechanical tissues in a stem of a grass . 99 



130. Mechanical tissues in a sunflower 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 



