The Coeorado Experiment Station 
H 
prove effective in controlling this pest. Although the grass' was 
very thin on the areas treated, it soon began to thicken, and by 
October 1 formed a fairly close sod. Nearly all of the white 
clover was killed by the two strongest solutions. 
The contrast between the treated and untreated areas was 
especially marked during the period of active blooming the next 
spring, the clear sod of the treated plats being surrounded by a 
thickly scattered growth of dandelions in flower. This effect was 
noticeable during at least three seasons following the application 
of the spray. 
Experiments in 1910 
In the spring of this year three plats, each 10x20 feet, were 
laid off on the College campus and treated as follows: Plat I 
sprayed four times, using a 10-percent solution o t iron sulphate; 
Plat II sprayed four times, using a 15-percent solution of iron sul¬ 
phate, Plat III, check plat, unsprayed. The sprayings were ap¬ 
plied April 25, May 5, May 17, and May 27, about one gallon of 
the solution being used for each 150 square feet of lawn at each 
application. The live plants on all three plats were counted the 
following spring, May 10, 1911, with the following results: 
Number of Plat. I II III 
Treatment . 10% iron sul- 15% iron sul- Check, untreated 
phate, 4 phate, 4 
spraying's sprayings 
Number of plants alive 
after one year. 200 209 1,574 
Percentage of live 
plants in terms of 
Plat III. 6.32 6.60 100 
According to the above, the weaker solution gave slightly bet¬ 
ter results than the stronger. This may be accounted for in part 
perhaps by the fact that the plants were apparently somewhat 
more numerous on Plats II and III than on I at the beginning of 
the experiment. The good effects of the sprayings on Plats I and 
II were apparent during at least three following seasons. 
Experiments in 1915 
During this year more varied experiments in the control of 
dandelions were conducted than before with special attention to 
the use of iron sulphate. A lawn of uniform character in which 
the dandelions had gained a considerable foothold was found and 
laid off into plats of 100 square feet each, the corners being mark¬ 
ed by small wooden stakes driven into the ground, level with the 
surface. A chalk line was tightly stretched along the boundaries 
of the plats and the dandelions within each area were carefully 
counted, including all sizes. The following table gives the treat¬ 
ment accorded each plat, together with the results in percentage 
of plants killed: 
