10 
BULLETIN 957, U. S. DEPARTMENT OF AGRICULTURE. 
States under the name R. aureum. This appears to be the form most 
common in cultivation in Europe, but the true R. aureum of the 
Rocky Mountain region and the plains of the Columbia was evi- 
dently introduced there soon after R. odoratum, if not at about the 
same time. Pursh may have referred to living plants of true R. 
aureum but we have no means of determining this. Lindley in 1828 
made the new species R. tenuiflorum (now R. aureum) and says 
"Clt. 1812," evidently meaning " cultivated in 1812." He had this 
so definitely distinguished from our R. odoratum that his statement 
is fairly conclusive that R. aureum actually was introduced into 
England the same year as was R. odoratum. The agent introducing 
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Fig. 9.— Outline map of the northeastern part of the United States, showing (by black dots and cross 
hatching) the known distribution of white-pine blister rust in North America to and including 1915. 
R. aureum can not be determined beyond question. There appears 
to be little doubt, because of the difficulty of communication at that 
time, that both plants were carried from their native regions to the 
eastern part of this country in the form of seeds. Cuttings may have 
been sent to Europe but it is more likely that seeds were sent. Seeds 
would not be likely to transmit a rust which does not attack the 
fruit. It does not seem possible that a fungus like Cronartium 
ribicola could be carried to Europe on these plants without becoming 
established in the Eastern States. Moreover, these species of Ribes 
apparently were introduced into Great Britain first. The fungus 
was not known in Great Britain until 1892, long after it was prevalent 
in other northern European countries. It appears that Cronartium 
ribicola was carried to Great Britain on infected white pines from 
northwestern Germany. The evidence appears to show that Cro- 
