174 BERRY— LOWER EOCENE FLORA OF [April 25, 



the largest alliance among the Choripetalae (Archichlamydese), and 

 next to the Compositse the largest angiospermous group, with over 

 9,000 existing species segregated among about 450 genera. 



There is a well-defined floral progression from the family Mimo- 

 sacese with its actinomorphic flowers and numerous, usually free, sta- 

 mens, through the Csesalpiniacese, culminating in the numerically 

 greatest group the Papilionacese with its strongly zygomorphic flow- 

 ers and coalescent stamens, comparable with the like culmination in 

 floral evolution of the Orchidaceae among the Alonocotyledonse. 



The Mimosaceae, with about 30 genera and 1,400 existing species, 

 are massed in the tropics of both hemispheres. None of the sub- 

 families are confined to a single continent but comparatively few 

 genera occur in more than two continental areas and half the genera 

 are restricted to a single continent. Asia and Australia each have 

 two peculiar genera, Africa has four and America has seven. Amer- 

 ica also leads in number of species, about half the total of the 

 family being present in the New World. Australia comes next with 

 over 300, Africa next with upwards of 300 and Asia last with about 

 100. In the eastern United States there are only three genera and 

 five species, none of which are arborescent. In the Gulf States the 

 numbers have increased to 14 genera and 44 species. 



The Csesalpiniacese with about 90 genera and 1,000 species is also 

 mainly tropical with a massing of forms in the American tropics 

 where there are over 600 species and 37 peculiar genera, the sub- 

 family Sclerolobiese being entirely American and containing numer- 

 ous monotypic genera. Asia and Africa each have about 150 spe- 

 cies. There are, however, only 10 Asiatic genera as compared with 

 17 African. There are but three Australian genera and less than 

 100 species. In the eastern United States there are 5 genera and 

 eleven species. Three of the genera, Cercis, Glcditsia and Gymno- 

 cladus are arborescent. In the southern states there are 11 genera 

 and 44 species. 



The Papilionacese have about 320 genera and 6.600 species. 

 America leads in the number of peculiar genera having 82 while 

 Asia leads in the number of species with about 1,700. Africa has 

 47 peculiar genera and about 1,600 species. Australia has 38 pecu- 



