DISTRIBUTION 



OF the thirty-four species of Azaleas enumerated here thirty-three 

 are widely scattered over the countries of the Orient having their 

 northern limit in central Hokkaido, their southern on Luzon in the 

 Philippines; from east to west they are found from the shores of the 

 Pacific Ocean in Japan to the extreme west of China proper. They 

 belong to four well-marked sections of the genus Rhododendron, two 

 of which (Tsutsutsi and Sciadorhodion) are peculiar to the Orient; 

 two (Rhodora and Pentanthera) are represented also in America. 

 The thirty-fourth species is R. luteum Sweet which belongs to the last- 

 named section. It grows in the Caucasus, the Pontus region of the 

 Black Sea and in Lithuania, Poland, and southwestern Russia, and is 

 the only species of the groups here discussed known to grow west of 

 China proper. 



Geographically the east Asiatic species are found over 45 degrees 

 of longitude and 30 degrees of latitude and altitudinally from sea-level 

 to about 3300 m. They are social plants and where climate and soil 

 conditions are favorable, as in most parts of Japan, of Korea and of 

 China from about the latitude of Shanghai south, these Azaleas are 

 perhaps the most common shrubs. The Chinese R. Simsii and R. Ma- 

 riesii grow also in Formosa, and a variety of the first-named is endemic 

 on the Kawanabe Islands off the northwest coast of the Liukiu Archi- 

 pelago. The Japanese R. serpyllifolium is said to grow on Okinawa, 

 the main island of the Liukius. At least three (R. Schlipperibachii, 

 R. Tschonoskii and R. Weyrichii) of the four Korean species grow also 

 in Japan. One (R. phoeniceum) is unknown in a wild state and is of 

 doubtful standing. The others are endemic in the different countries 

 of the Orient. 



It is remarkable that in western China only the section Tsutsutsi 

 with three species is represented, and on the Himalayas no member of 

 the four sections is known to grow, yet in these two regions the sub- 

 genus Eurhododendron has its headquarters and is represented by 

 hundreds of species. In Malaysia, too, where the subgenus Vireya is 

 so richly represented, no species of our subgenus is known. The great 

 concentration of species is in Japan. Formosa, considering its small 



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