mixture did not materially lessen the blight, and the microscopic 
plants which cause these leaf diseases are not commonly found asso¬ 
ciated with this trouble. We conclude, therefore, that the premature 
dying of the potato vines is usually an evidence that the underground 
parts have been severely injured by the fungus in question. 
Running Out. The running out of potatoes, as it is called when 
the tubers become pointed or much elongated, appears also to be as¬ 
sociated with the attacks of this fungus. But just what the relation 
is between the two has not yet been determined. 
Treating the Seed. At first thought it would appear to be a 
simple matter to combat this disease by treating the seed with for¬ 
malin or corrosive sublimate. In fact, some of our experiments with 
treated seed have shown decided gains, but others have given a loss. 
The results of this season are again negative, so it is doubtful if the 
seed treatment can be made to pav. This is true for the reason that 
most Colorado soils are thoroughly infected with the fungus and 
the treatment usually delays the sprouting of the seed and conse¬ 
quently injures the plant so that it does not yield as well as un¬ 
treated seed. 
Seed Selection. Better results have been secured bv selecting 
smooth, round seed that was entirely free from disease. Such pota¬ 
toes are not only free from disease, but the chances are that they 
were grown on vines that were not seriously affected by the fungus 
as run out potatoes usually occur on diseased vines. We would ex¬ 
pect such seed to show a certain degree of resistance to the disease. 
Disease-Resistant Varieties. The only prospect that we now 
have of ever overcoming this disease beyond what can be done by 
improved methods of culture, is to select seed from the healthiest 
plants that produce good shaped tubers, and thus gradually breed 
up a resistant strain. Last year over 80 varieties of potatoes were 
grown in the College garden in soil that was known to be badly dis¬ 
eased. Only 20 kinds out of this number were saved for further 
testing; the rest produced only a few small, misshapen tubers, and 
many of the vines bore none at all. This year the list has been still 
further cut down, though a few varieties yielded well. These were 
all dug by hand, and the hills that produced the best tubers have 
been saved for further testing. We hope in time to build up a strain 
of potatoes that will resist the attacks of this fungus by selecting 
from individual hills that are the least attacked by disease. 
Not many potato growers can afford the time to follow up ex¬ 
periments of this kind, but a less rigid method of selection could be 
practiced by all. The following is quoted from Bulletin 91, of this 
Station: / , ' ] ! 
“Another method which gives evidence of considerable practical value 
is to set aside each year five or ten acres of land for the growing of seed 
