322 PLANTS, SEEDS, AND CURRENTS 



that in the derivative families the process of differentiation has often 

 proceeded so far that the original family type is lost, being only non- 

 represented in the characters uniting in one great plant-group a 

 number of families, which, although they hold the world between 

 them, respectively characterise different portions of it. In the 

 family, in the tribe, in the genus, in the species, in the variety, and 

 in the local race, we see the same principle at work, the process 

 being illustrated in its last stage in the role of the polymorphous or 

 highly variable species (pp. 313-14). 



3. Whilst we should expect to find a primitive family represented 

 in all the continents, the absence of some of the derivative families 

 is often to be looked for. To illustrate the argument we may take 

 the flora of Australia, where there are world-ranging families, bearing 

 a special Australian impress, associated with families of later develop- 

 ment and of Australian origin, which represent an extensive regional 

 modification of a primitive world-ranging type that has been lost in 

 the differentiating process (pp. 315-16). 



4. In this connection attention is drawn to recent papers by 

 Mr. E. C. Andrews on the development of the Myrtacece and Legumi- 

 nosce with special reference to Australia. Adopting the view that 

 the evolution of floras represents the response of plant-life to its 

 physical environment during ages of changing geographical sur- 

 roundings, he applies it to the differentiation of these two families 

 from wide-ranging primitive forms of the Cretaceous period when 

 relatively uniform climatic conditions prevailed. He challenges the 

 correctness of the older determinations of Eucalyptus remains in the 

 Cretaceous and Tertiary deposits of the northern hemisphere, and 

 claims the genus as Australian-born (pp. 317-19). 



5. With this digression the author goes on to show that if the 

 differentiation hypothesis is correct no natural order could have 

 been developed on the lines implied in the Darwinian theory, which, 

 as interpreted in recent works, begins with the variety and termi- 

 nates with the order, a process that reverses the usual method of 

 nature (pp. 319-20). 



6. Yet such a process, as is there implied, is common enough in 

 the plant- world; but it accounts not for natural orders, but for all 

 the oddities of plant-forms. It is here termed a specialising process 

 in contrast with that of differentiation ; but it is the differentiating 

 process that has been the principal determining cause of diversifica- 

 tion in plants (p. 320). 



