XIV CONTENTS 



PAOB 



§ 154. Annuals 113 



§ 155. Biennials 114 



§ 156. Perennials 114 



§ 157. Changes in the length of life of a species . . . 115 



§ 158. Buds 115 



§ 159. Naked buds 116 



§ 160. Scaly buds 116 



§ 161. Buds of the apple 117 



§ 162. Buds of elder, maple, or elm 118 



§ 163. Sleeping buds 118 



§ 164. The awakening of sleeping buds 118 



§ 165. Winter buds of aquatic plants 119 



§ 166. Behavior of the hibernacula 120 



§ 167. Bulbs 121 



§ 168. Corms 121 



§ 169. Forcing or inducing an earlier growth .... 121 



§ 170. Some protective devices of the shoot . . . .122 



§ 171. Branches used as leaves 124 



§ 172. The part of stems in the struggle for existence . . 124 



§ 173. Weeds 125 



§ 174. Climbing plants 125 



§ 175. The irritability or sensitiveness of stems .... 127 



§ 176. Sensitiveness to gravity 128 



§ 177. Stems are found among the higher plants only . . 129 



VII. The Way in which New Plants Arise 



§ 178. Distribution of the individuals of a species . . . 130 



§ 179. Methods of reproduction 131 



§ 180. Reproduction by cuttings 132 



§ 181. The stem may reproduce the entire plant . . . 132 

 § 182. The root may reproduce the entire plaut .... 132 

 § 183. Structures used by plants as means of vegetative repro- 

 duction 133 



§ 184. Tubers 133 



§ 185. Bulbils and bulblets 134 



