xii CONTENTS 



PAGE 



206. Fundamental Methods of Evolution 191 



207. Origin by Adaptation 192 



208. Origin by Variation 195 



209. Origin by Mutation 196 



210. Origin by Hybridation 197 



Experiment 58. The Occurrence of New Forms in Nature 198 



211. Natural Selection 198 



212. Isolation 199 



213. Polygenesis 199 



214. Experimental Evolution 201 



CHAPTER X 

 METHODS OF STUDYING VEGETATION 



215. The Study of Vegetation 202 



216. The Quadrat 202 



217. Kinds of Quadrats 203 



218. Marking out Quadrats 204 



219. The List Quadrat 204 



220. Abundance 205 



221. The Chart Quadrat 205 



222. Making Quadrat Charts 206 



223. The Permanent Quadrat 208 



224. The Denuded Quadrat 209 



225. Transects 210 



226. The Line Transect 210 



227. The Belt Transect 211 



228. The Migration Circle 212 



229. Formation Maps 213 



CHAPTER XI 

 THE PLANT FORMATION 



230. The Nature of Formations 215 



231. Recognition of Formations. 216 



232. Relation between Habitat and Formation 218 



233. The Historical Factor 219 



234. Development and Structure 219 



235. Structure of the Formation 221 



236. Facies 221 



237. Principal and Secondary Species 222 



238. Aspects 223 



Experiment 59. Study of Abundance and of Aspects 224 



239. The Parts of a Formation: the Consocies 225 



240. The Society 226 



