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believed to be very distinct, since the idea prevails that they 
would not survive the winters of the northern limit of the 
Juglans nigra range, 7.e., in South Dakota or Minnesota. 
In some horticultural publication in long years past (I think 
it was by L. H. Bailey, although much searching has not located 
it), I recall reading of an experiment with black walnut bearing 
on this very point. Nuts from trees in southern Illinois were 
planted in northern Illinois and the seedlings from them winter- 
killed. Nurserymen of the northwestern states (South and 
North Dakota, Minnesota) commonly regard Vermont apple 
seed as more desirable for raising seedlings for grafting purposes 
than that which comes from France, because seedlings from the 
former are less liable to winter-kill. Yet both kinds of seed 
come from the same apple species. 
Strains of the same species of alfalfa vary remarkably in their 
winter-hardiness, as was demonstrated by experiments with 
several hundred varieties at Edgeley, North Dakota. According 
to Arny (1924), strains of red clover from France, Chile, and 
Italy winter-killed 81 per cent., 89.5 per cent., and 93.8 per cent. 
respectively, when grown in Minnesota, while seed from the north- 
ern tier of states, grown under the same conditions, gave a much 
lower percentage of winter-killing. Mr. Russell Silvers, of Hicks- 
ville, N. Y., personally told me of a striking case of a plant of the 
Virginia creeper, Parthenocissus quinquefolia, from Cuba, indis- 
tinguishable from our common northern type, which winter- 
killed when grown outdoors in New York. 
Many other cases similar to those above might be given as 
evidence favoring the belief and horticultural practice that 
varieties, strains, and geographical forms within a species vary 
considerably in their ability to resist cold. Horticulturists and 
gardeners are well acquainted with this body of fact. 
Natural selection is commonly credited with originating these 
differences, but it is generally understood that each species has a 
limit within which it varies as regards its ability to withstand cold. 
Thus species and their forms and varieties are designated hardy, 
half-hardy, and tender, usually with reference to a given locality 
such as the Arnold Arboretum or to a given region as the northern 
great plains area of the United States, or the sub-tropical regions 
of Florida and California. Altitude, winter humidity, winter 
