70 HORTICULTURAL SOCIETY OF NEW YORK. 



although they appear to be similar in all observable botanical 

 characters. Russian foresters called our box elder tender, the 

 seed having been gathered near St. Louis, Missouri ; but when 

 they secured seed from pure native trees in Manitoba they 

 found the trees to be perfectly hardy at the north. They named 

 this variety "Boreale," indicating its northern origin ; as yet we 

 have not waked up enough here to make this distinction as far 

 as I am aware, and the average planter is blissfully ignorant 

 as to whether the box elder he plants dates back to Arkansas, 

 Manitoba, Missouri or North Dakota. 



It has been found by many northern nurserymen that the 

 red cedar of the South is tender and short-lived at the North, 

 while the local northern form of the species is hardy. 



Robert Douglas learned many years ago in northern Il- 

 linois that the black walnut of the South was tender at the 

 North, whereas the local northern form was hardy. He also 

 determined that there was a decided difference in hardiness on 

 exposed prairies of the conifers from the Rocky Mountains ; the 

 forms of various species from the Pacific slope side being much 

 inferior in hardiness to those from the eastern slope. 



In the course of three trips to Russia I learned that Rus- 

 sian foresters had found the Scotch pine from western Europe, 

 and from France and Germany, inferior in hardiness to the 

 Scotch pine of northern Russia and extending into Siberia. 

 Similar differences have been noticed between the west European 

 and the east European and west Siberian form of the Norway 

 spruce. 



Many more instances .might be given of the fact that a spe- 

 cies extending over a wide geographical range, varies widely in 

 its capacity to resist cold. It shows then that nature must have 

 done a work in acclimating plants so that it will endure a greater 

 degree of cold. 



DeCandolle. in his "Origin of Cultivated Plants," states: 

 "The northern limits of wild species . . . have not changed with- 

 in historic times, although the seeds are carried frequently and 

 continually to north of each limit. Periods of more than four 

 or five thousand years, or changements of form and duration, 

 are needed, apparently, to produce a modification in a plant 



