198 E. C. Andreios—Tlie Geological History of the 



The genera Castanospemum and Podopetalum, in Sophorese, 

 were developed in the Australian jungles after the isolation of 

 Australia, but these genera are monotypic and probably repre- 

 sent decadent genera, despite the fact that the individuals are 

 luxuriant types. Sophorea?, indeed, appears to be a decadent 

 tribe which, however, possesses a powerful and vigorous 

 offshoot, the Podalyrieas. 



Acacia also is a magnificent example of the adaptation 10 of 

 a tree with bi-pinnate leaves to a hungry sandstone setting 

 by the rejection of its leaves and the development of phyllodes. 

 The formation, later, of the great soil plains of the central 

 areas, and of the plateaus of the eastern areas of Australia, 

 gave the new vigorous subgenus a further field for its energies. 



(3) Myrtacece. 



This is a family less elastic than the Leguminosse in accom- 

 modating itself to a harsh and severe environment, and from 

 the point of view of distribution it is to be compared with 

 the Mimosacese or the Csesalpiniaceae rather than with the 

 Papilionacete. 



In the tropics the more primary types Eugenia (in the 

 Benthamian sense) and Myrtus are widely spread and suggest 

 former direct land connections between all the great land 

 blocks, this older interchange of fertile types in regions of 

 mild and moist climate, however, having ceased long since. 



In tropical and subtropical America, after the zoning of the 

 climate ensued, the Myrtacese were modified gradually with 

 the development of the true Eugenias, Myrcia, Calyptranthes, 

 Marlieria, and other types. According to Berry 17 the genus 

 Myrcia contains about 450 species, and represents one of the 

 older, or primary, Myrtacea?. . But the type does not exist 

 outside America, and, moreover, it is a vigorous, vast, and 

 aggressive genus, which is confined to one compact area, hence 

 it seems unlikely that it is as old as Eugenia, or Myrtus, which 

 occur abundantly in all the large land blocks with the exception 

 of Europe and America north of Mexico. 



All of these American types belong to the tribe Myrtce, no 

 other tribe of the family having been developed in that country. 



In Australia, however, the great areas of hungry, sandy soil, 



10 E. C. Andrews, The Distribution and Development of the Natural 

 Order Leguminosae, Proe. Roy. Soc. N. S. Wales, vol. xlviii, 1914. 



17 E. W. Berry, The Affinities and Distribution of the Lower Eocene Flora 

 of South Eastern North America, Proc. Amer. Phil. Soc, vol. liii, pp. 222- 

 227. 1914. 



