PREFACE 



The value of Azaleas as garden plants in the eastern United 

 States, where few of the Rhododendrons with persistent leaves 

 can be successfully cultivated, has led to the critical studies of 

 these plants which appear on the following pages. 



Mr. Wilson's long journeys in eastern Asia has made it pos- 

 sible for him to study all the species of the Japanese Empire 

 and China as wild plants, and to become familiar with the 

 Azaleas growing in Japanese gardens. For many years the 

 Arboretum has been engaged in a field study of the American 

 species, and has been able to place at Mr. Rehder's disposal 

 the large amount of material which is preserved in this her- 

 barium, and which has been supplemented by that contained in 

 other American collections. 



The Azaleas of northern Japan and Korea, and of the 

 northern United States, are already growing in the Arboretum, 

 but the gardens of the southern states and of California have 

 still much to gain by the introduction of the species of the 

 southern states and those of southern Japan, China, and 

 Formosa, and this publication will not have accomplished its 

 purpose if it fails to induce the more general cultivation of 

 these plants in the United States and Europe. 



The art of the hybridizer has produced many interesting and 

 beautiful Azaleas. Imperfect records have made the study of 

 many of these hybrids difficult and uncertain, and this difficulty 

 is increased by the fact that many of them are no longer culti- 

 vated unless, having escaped the change of fashion in plants, 

 they are still growing in English gardens, planted about the 

 middle of the last century, and I venture to suggest to my 

 associates in the English Rhododendron Society that the study 

 of Azaleas in European gardens might add much to the knowl- 

 edge of the origin and value of many of these plants. 



C. S. Sargent, Director. 

 Arnold Abbohetum 

 March, 1921. 



