182 BERRY— LOWER EOCENE FLORA OF [April 25, 



first of these, the Rutacese, consists of about iii genera and over 

 900 existing species widely distributed over the warm temperate and 

 tropical regions of the earth. The fruits are capsules, samaras or 

 drupes and the leaves which may be simple or compound are usu- 

 ally glandular punctate. While there are 34 genera with 127 species 

 confined to America the family makes its greatest display in the Old 

 World, Africa having 16 peculiar genera with 196 species and Aus- 

 tralia 28 peculiar genera with 185 species. In addition to 6 genera 

 with 7 species confined to the Asiatic Mainland there are 19 genera 

 with 167 species found distributed from southeastern Asia through 

 Malaysia greater or less distances, in some cases to New Zealand 

 and Polynesia. The only truly cosmopolitan genus is Fagara with 

 upwards of 150 existing species and represented in all tropical 

 countries. The tribe Boroniese with 18 genera and 158 species is 

 confined to i\ustralia and New Zealand; the Diosinese with 11 genera 

 and 181 species is confined to South Africa; and the Cuspariese with 

 16 genera and 83 species is confined to tropical America. All of the 

 other rather numerous tribes are represented in more than one con- 

 tinental region. 



The family contains the remarkable number of 42 monotypic 

 genera and while many of these may be regarded as of recent evolu- 

 tion, as for example a number of those of Australia, the isolated 

 occurrences of many of the others indicates that they are of great 

 age and once occupied intervening areas. 



There are only twelve known fossil genera, or only about 10 per 

 cent, of the existing genera, so that little can be said of the fossil 

 history of the family. The oldest genus is CitropJiyUum Berry rep- 

 resented by very characteristic leaves with alate petioles found in 

 the Dakota sandstone of the Rocky Mountain province and from 

 New Jersey to Alabama along the Atlantic coast in the Raritan, Mag- 

 othy, Middendorf and Tuscaloosa formations. There is a second 

 species of Citrophyllum in the Wilcox and a third in the overlying 

 Claiborne. These forms are very similar to the leaves of recent 

 members of the Aurantioideae and undoubtedly represent ancestral 

 forms. The genus Dictamniis Linne with a single existing species 

 widely distributed in Eurasia, has furnished a fossil form in the 

 Pliocene of France and a second in the Pleistocene of Japan. Unge 



