31 
fectly hardy. Trees of this same species over 50 years old, ob- 
tained from planting nuts from southern Indiana, are described 
by the same writer as hardy near Richmond Hill, Ontario, al- 
though they do not bear nuts except in the most favorable sea- 
sons. Z. H. Ellis, in the same volume, describes his experiments 
with pecans at Fair Haven, Vt. Most of his many attempts re- 
sulted in the seedlings winter-killing the first winter, but he has 
one tree, over 30 feet tall and a foot in diameter, that grew from 
seed obtained in Vermont. He states that it is the only pecan tree 
in his state. Recently, a 25-year-old Para rubber tree (Hevea 
eee has been discovered in an unprotected situation near 
Palm Beach, Florida (Official Record, U. S. Dept. Agric. 5: 39, 
1926). Dunne this growth period, the account states, it must 
have withstood temperatures below freezing, perhaps as low as 
24° F. to 28° F., and yet farther south, at Miami, there are 
records of trial plantings of this same species that apparently 
died from too low temperatures. Many less striking cases in 
other plants might be described, but these are reserved for a 
more extended and detailed account on this whole problem. 
Here, I wish to bring out two more points which have to do 
with this problem. In searching for data, I thought the floras 
of various rivers might help, particularly those that flowed from 
a frost-free or subtropical region into a much colder one. But 
apparently there are no such rivers. They all flow from a cold 
region into a warm region, as most of the tropical rivers do, or 
from a relatively cold into a much colder region, as in the case 
of those flowing into the Arctic Ocean. In no case were rivers 
found flowing through enough ranges in temperature to make 
their floras significant for this problem. 
The second point has to do with the ability of woody or her- 
baceous perennial plants to acquire immunity to cold without 
changing their hereditary constitution. M. J. Dorsey and J. W. 
Bushnell (The hardiness problem, Minn. Agric. Exper. Sta. 
Jour. Ser. Papers 242, p. 9) discuss this question in connection 
with the experiments of J. C. Whitten. Whitten obtained buds 
of Elberta and Old Mixon Free peach varieties from trees at 
different points between Michigan and Texas, and grew them at 
Columbia, Mo. In all cases, the trees grown from buds of the 
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