1922] SARGENT, FIRST FIFTY YEARS OF THE ARNOLD ARBORETUM 171 



produced shrubs which are the chief ornament of many gardens. Less has 

 been done in attempting to improve trees by the mixing of different species. 

 Hybrid trees especially among Oaks often occur in this country. Several 

 of these trees are already in this Arboretum where they grow more rapidly 

 and are often hardier than their parents. Natural hybrids of Poplar-trees 

 are common and often grow more rapidly than their parents ; and a number 

 of hybrid Poplars have been raised artificially in Europe and promise to 

 become valuable trees. One of the largest, hardiest and most rapid-grow- 

 ing of all Elm- trees is a natural hybrid between two European species. 

 The best Hickory- nuts are produced by trees which are natural hybrids; 

 and one of the largest and handsomest hybrid Oak-trees in the United 

 States has also been artificially reproduced by crossing the two species which 

 were the parents of the natural hybrid. Judging by what little is now 

 known about hybrid trees it does not seem improbable that new races of 

 trees may be produced artificially which will contribute materially to the 

 value of the forest products of the world and increase the beauty of parks 

 and gardens. The Arnold Arboretum with its great collections and its 

 connection with the principal cultivators of plants is now the best place for 

 breeding new trees and shrubs in the United States. Plant breeders from 

 all parts of the country send to it for the material needed in their work but 

 this work can best be done here. 



Fifth : A Rose Garden and a Rock Garden if planned comprehensively 

 would add much to the horticultural value of the Arboretum, and bring 

 many visitors to it. 



Only a larger endowment is needed to make possible these Arboretum 

 activities and extensions. 



