286 /:'. ( '. Amlfiirs — 'flic (l<ol<><jical History of the 



few Australian types, however, the shrubby habit is still 

 retained and the leaves may he compound or simple. These 

 herbs and dwarfed forms characterize the cool and cold tem- 

 perate regions, but in Australia certain large and endemic 

 genera are xerophytic and occur on the hungry sandy soils of 

 warm and cool temperate Australia. The Cornacese are mainly 

 trees and shrubs adapted to the cooler temperate regions and 

 with leaves simple or compound. 



From this it may be conjectured that the ancestral forms of 

 the Umbelliferae were trees of luxuriant habit, with compound 

 leaves, and lovers of mild and moist climate, that upon an 

 early differentiation of climate, probably in the Cretaceous, 

 the Umbelliferae were developed in open and well-watered 

 regions after the wide dispersal of the ancestral forms and while 

 these earlier Umbelliferae were still trees or shrubs. These 

 types reached Australia apparently during some portion of the 

 Cretaceous and at a later date, after the great isolation of 

 Australia from the rest of the world, while the Australian 

 plants were faced with the gradually approaching but pro- 

 nounced climatic differentiations, these early Umbellifers found 

 a refuge on the large barren sandy tracts, which sandy wastes 

 at the same time were causing new large and aggressive genera 

 to spring up among the Myrtacese, Leguminosse, Labiataa, 

 Euphorbiacea?, Epacridacese, Goodeniacese, Candolleacese, Pro- 

 teaceae, Dilleniacese, and other families. In this favorable set- 

 ting the large endemic genera XantJwsia, Trachymene, Siebera, 

 and Didiscus, were developed, as also the strange and beautiful 

 Actinotus. All these are strongly xerophytic and belong to the 

 same great period of evolution in Australia which produced 

 the Eucalyptus, Goodenia, Leucopogon, the ph yllodineous 

 acacias, and other types, which all flourished together on the 

 waste sandy tracts of the island continent. A very few of 

 these xerophytes bear distinct traces of their old shrubby or 

 arborescent habit, such as Trachymene Bittardieri, which is a 

 low shrub. In the north these early types of the Umbelliferae 

 were subjected afterwards to the great late and post-Tertiary 

 differentiation, and the forms which had already been expelled 

 in great part from the mild and moist region during the first 

 great differentiation, were reduced to herbs during this second 

 stage, and others being converted to hardy, vigorous, and aggres- 

 sive types in the northern hemisphere, they commenced their 

 way southwards sending off shoots along the American moun- 

 tains to Chili and Antarctic South America. Thence some of 

 them appear to have been carried by sea currents, by birds, or 



