12 BULLETIN 1451, U. S. DEPARTMENT OF AGRICULTURE 
should cause a minimum of damage to harmless vegetation and to the 
soil subjected to the treatment. 
EXTENT AND LOCATION OF EXPERIMENTS 
The experiments with chemicals reported in the following pages 
were begun in the fall of 1921 and continued up to the summer of 
1925, a period of more than three and one-half years. All labora- 
tory and greenhouse tests were made at the University of Wisconsin, 
Madison, Wis. Many chemicals were tried in the greenhouse in 
winter on small potted barberries. (PI. 7, B.) This was continued 
as an easy, quick method of testing in a preliminary way other 
chemicals that were added to the list from time to time. The potted 
plants were portions of roots or portions of shoots with some roots 
taken from large bushes in the field. Most of these cuttings grew 
readily and produced an abundance of small roots as well as thrifty 
shoots. They were potted for the most part in 8-inch flower pots 
in rich loam and were used when the shoots were 12 inches or more 
in height. Several plants commonly were used for each test, and 
controls always were kept. 
It was calculated that 5 grams of a chemical applied to a bar- 
berry plant growing in an 8-inch pot was equivalent to 1 pound 
applied to a bush not over 12 inches in diameter at the base grow- 
ing in the field. Approximately 40 cubic centimeters of a solution 
applied to a barberry growing in an 8-inch pot was considered 
equivalent to an application of 1 gallon in the field. It is evident 
that these estimates of the quantity of any chemical applied in the 
field which would be equivalent to a certain application to a potted 
barberry are only approximate. The results showed that the action 
of a chemical applied to a barberry in the field can not be predicted 
with certainty from tests with the same chemical in the greenhouse. 
Nevertheless, the method is a convenient one and serves as an indi- 
cator of what may be expected in the field. 
The field operations were of two kinds: (1) Treating with a series 
of chemicals a series of individual, marked barberry bushes grow- 
ing naturally in the field and of as nearly the same size as possible ; 
(2) treating with one chemical all the barberries growing in a cer- 
tain area. 
The individual bushes used for testing the chemicals were in 
Dane County. Wis., and Lake County, 111. In Dane County es- 
caped bushes growing on several farms a few miles south of Black 
Earth were used. This area was rather hilly. Limestone under- 
laid the soil, and there were frequent outcroppings of this rock on 
the hillsides. In another location in Dane County barberries were 
treated on a farm about 1 mile north of Marshall. * Here a barberry 
hedge surrounded a small orchard. These bushes were treated, as 
were also many escaped bushes in a near-by pasture. (PI. 9, B.) 
When no more suitable bushes were available in these two areas 
bushes were selected on two farms about 2 miles northwest of Gur- 
nee, Lake County, 111. This area, in which barberries of unknown 
origin were growing wild on about 50 acres of wooded pasture land, 
is nearly level and has a rich loam over gravel. 
More than 2,G00 separate marked bushes of approximately uni- 
form size and character were treated in these three areas. The 
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