INTRODUCTION xxiii 



of this group growing on the Himalayas. The monotypic Planera 

 occurs only in eastern North America, and Pteroceltis and Zelkowa 

 have no American representatives. Celtis is common to the two 

 regions, but the trees of this genus are larger and appear to be 

 more generally distributed in eastern North America than in 

 eastern continental Asia. The tropical genus Trema is represented 

 in both regions. 



Horaces. — Of this family the monotypic Madura is American, 

 and Broussonetia, Cudrania, and Artocarpus, which occur in China, 

 have no American representatives. There are two species of Morus 

 in each of the two regions, but neither of the two American Mul- 

 berries compare in value with the Chinese Morus alba L., for the 

 leaves of this tree and its numerous varieties furnish the best and 

 chief food of the silkworm in all countries where silk is made. In 

 Ficus the advantage is with China, both in the number of species 

 and in the size of individuals, only two species having secured a 

 foothold in tropical Florida, where they are comparatively small 

 trees. Its nearness to tropical south-eastern Asia, which is one 

 of the great centres of distribution of this genus, will account 

 for the presence of some forty species of Ficus in southern China, 

 where some of the species grow to a very large size. 



Proteace^. — Helicia, in south-eastern China, is the only genus 

 represented in the floras of the two regions. 



LoRANTHACE^. — Inthis family Phorodendr on is North American; 

 Arceuthobium is North American and Japanese, and Loranthus and 

 Viscum are found in China and not in eastern North America. 



Santalace^. — Pyrularia and the monotypic Darbya have not 

 been found in China. Henslowia is eastern Asiatic, and Buckleya 

 has a representative in the floras of the two regions. 



OpiLiACEiE. — One species of the tropical genus Cansjera, in 

 south-eastern China, is the only woody member of this family in 

 our two regions. 



Olacace^. — Of this tropical family Schoepfia and Ximenia have 

 reached southern Florida from the West Indies, each with a single 

 species ; in China it appears only in Schoepfia. 



Aristolochiace^. — This family is represented in the floras 

 of the two regions by the genus Aristolochia, with more numerous 

 woody species in China than in eastern North America. 



PoLYGONACE.E. — No arboresccut or shrubby species of this 

 family is reported in China, but in tropical Florida two species of 

 Coccolobis occur, and a species of Brunnichia is widely scattered 

 through the southern United States. 



