Australian Flowering Plants. 179 



or do they imply merely a response by the plants to their 

 environment of extremely poor soil? 



Before proceeding to the general discussion of these points, 

 however, it will be advisable to mention briefly the significance 

 of the general relationships existing between the families and 

 orders of the flowering plants, the significance of the Cre- 

 taceous and post-Cretaceous geography and climate, of the 

 transporting agency of man, animals, and the sea, of vigorous 

 and aggressive plant genera, of the distribution of mammals, 

 and of the theory of multiple origins. 



II. The Significance of the present Relationships existing 

 between Families and Orders of the Flowering Plants. 



The angiosperms are divided into about two hundred and 

 fifty families, according to the various classifications proposed 

 by systematists. These families are fairly distinct from each 

 other but they may be grouped into series yet more distinctive 

 known as orders. With a few exceptions the many orders are 

 quite distinct from each other. If now the orders be taken 

 individually it will be found that, in most cases, they possess 

 some families characterized by tropical arborescent forms, 

 generally also of luxuriant appearance, while other families 

 in the same order are mainly herbaceous and confined to the 

 cooler, or colder, regions of the earth. This is most pronounced 

 in the more highly specialized types such as the Sympetalse 

 and the more specialized of the Dialypetalese types, while it 

 is less pronounced in the more primitive types of the Mono- 

 chlamydese, such as the catkin-bearing groups. Thus the 

 Araliacese and the Umbelliferse with the Cornacese form an 

 order, in which the Araliacese, for the most part, are luxuriant 

 trees suggestive of the tropics or sub-tropics while the Umbel- 

 liferse are herbs, for the main part, in the cooler portions of 

 the globe, their extremely compound leaves, however, suggest- 

 ing an ancestry flourishing under mild and moist conditions. 

 The Rubiacese, the Stellatse (Lindley), and the Caprifoliacese, 

 form another distinctive group, in which, however, the Capri- 

 foliacese have preserved their woody nature even though 

 acclimatized to the cold. For the Leguminosse, which embraces 

 the Papilionacese, Caesalpiniacese, and Mimosacese, an ancestry 

 of large trees is suggested with luxuriant pinnate foliage, with 

 a tendency to adapt itself to temperate climates on the part 

 of the Papilionacese, especially in the cases of the herbaceous 

 tribes Viciese, Trifoliese, and Lotese. The Gruinales, com- 

 prising families such as Rutacese, Geraniaceas, Oxalidacese, 



