CONTENTS OF THE INTRODUCTORY ESSAY. 



§ i. 



Preliminary Remarks. 



PAGE 



Sources of Information, published and unpublished, materials, collections, etc i 



Object of arranging them to discuss the Origin, Peculiarities, and Distribution of the Vegetation of Australia, 



and to regard them' in relation to the views of Darwin and others, on the Creation of Species .... iii 



§ 2- 



On the .General Phenomena of Variation in the Vegetable Kingdom. 

 All plants more or less variable ; rate, extent, and nature of variability ; differences of amount and degree 



in different natural groups of plants v 



Parallelism of features of variability in different groups of individuals (varieties, species, genera, etc.), and 



in wild and cultivated plants vii 



Variation a centrifugal force ; the tendency in the progeny of varieties being to depart further from their. 



original types, not to revert to them viii 



Effects of cross-impregnation and hybridization ultimately favourable to permanence of specific character . x 



Darwin's Theory of Natural Selection ; — its effects on variable organisms under varying conditions is to give 



a temporary stability to races, species, genera, etc xi 



h 3. 

 On the General Phenomena of Distribution in Area. 



Circumscription of Area of Species, and causes of it xii 



Relative Distribution of Natural Groups of Plants xiii 



Insular Ploras, and analogies between them and mountain Floras, and between the geological ages of insular 



and other Ploras xv 



Existing conditions will not account for existing distribution . xvi 



Effects of Humidity in modifying distribution : — effects of the Glacial Epoch, and Darwin's views thereon . xvii 



§ 4. 

 On the General Phenomena of the Distribution of Plants in Time. 



Outlines of the principal facts in Possil Botany xxi 



Their bearing on the question of Progressive Development amongst known Plants xxii 



Progression and Ptetrogression of A r egetable Types xxiv 



