xxxiv A NATURALIST IN WESTERN CHINA 



well illustrates, perhaps, the differences in the floras of the two 

 regions as Rhododendron. In eastern North America there are 

 only six species of true Rhododendron, all confined to the extreme 

 eastern part of the continent, and, with one exception, of restricted 

 range, but some one hundred and sixty species have already been 

 distinguished in eastern continental Asia, where the genus is widely 

 distributed and where, on the mountains of the western and south- 

 western provinces, is the greatest segregation of these plants in the 

 world. On the other hand, only three species of Azalea have been 

 found in China, while in eastern North America, which is the 

 region of their greatest development, ten or twelve species are 

 recognized. 



Theophrastace^. — The only member of this family in the 

 floras of the two regions is a single species of Jacquinia in tropical 

 Florida. 



Myrsinace^. — ^This family has a much larger representation 

 in eastern continental Asia than in eastern North America, only one 

 species each of Ardisia and Rapanea having reached tropical 

 Florida, while in southern China there are several species of Ardisia, 

 Rapanea, and Myrsine, and where also Msesa, Embelia, and ^giceras 

 occur. 



Plumbaginace^. — With Plumbago in the two regions the 

 family is also represented in China by Ceratostigma. 



Sapotace^. — In this family eastern North America has the 

 advantage with six genera, while only three genera reach southern 

 China. Of these only Sarcosperma is not represented in the 

 American flora. The other genera which are found in China, 

 Sideroxylon and Chrysophyllum, occur in tropical Florida, which 

 has been reached also by Dipholis and Mimusops, while Bumelia, 

 which is an American genus, is widely distributed through the 

 southern United States with several species. 



Ebenace^. — Of this family only one genus, Diospyros, is 

 represented with two species in eastern North America, and eight or 

 nine species in China. As a fruit tree one of the Chinese species 

 is much more valuable than the North American species. 



Styrace^. — Of this family Styrax occurs in the two regions. 

 Halesia, with three species, is eastern North American ; and the 

 monotypic Alniphyllum and Pterostyrax are Chinese. 



SYMPLOCACEiE. — Symplocos, the only genus of the family, 

 appears with one species in the southern United States, and is 

 largely represented in China, where twenty species are distin- 

 guished. 



