well as many tree groups, including the willows, poplars, 
maples, cherries, elms, and ashes, were excluded from the 
Garden. Since 1936, new collections of these groups have 
been planted within the present area and a large number 
of additional groups have been added. The present enu¬ 
meration records 2,889 species and varieties. This figure 
does not include more than one hundred kinds of plants 
being raised from seed collected by the 1938 Hu expedi¬ 
tion to China, nor certain other plants that are not yet 
identified. New material is constantly being added to the 
collections of hardy trees and shrubs. Every effort is made 
to keep the plants clearly labeled. 
NAMES 
The nomenclature adopted in this handbook follows 
essentially that used by Alfred Rehder in his “Manual of 
Cultivated Trees and Shrubs” (1940 edition).* Where a 
name in the * 94 ° edition of Rehder differs from that used 
in the 1927 edition or from that favored by Bailey in “Hor- 
tus Second, the alternate name appears here as a synonym 
in parentheses. Common names are given only when they 
are listed in Rehder’s “Manual” or in “Hortus Second.” 
* The following publications have also been consulted: “Kew Hand-list of 
Trees and Shrubs,” 1934; “Kew Handlist of Coniferae,” 1938; “Index 
Kewensis”; “Trees and Shrubs Hardy in the British Isles” by W. J. Bean, 
1919-33; “Cultivated Lilacs” by Susan D. McKelvey, 1928; “The Oriental 
Flowering Cherries” by Paul Russell, 1934; “Yearbook of the Rhododendron 
Association, 1939; “The Species of Rhododendron” published by The 
Rhododendron Society [Edinburgh], 1930; “Rhododendrons and Azaleas” by 
catalogs U ■ Bowers ’ 1936; and numerous seed-exchange lists and nursery 
VI 
