20 
The Colorado Experiment Station 
er solution, made by dissolving the iron sulphate in water, at the 
rate of .pounds to a gallon, is practically as effective as this 
stronger solution, is less apt to injure the grass, and is a little 
cheaper. 
Time and Frequency of Spraying .—From the experiments 
tried here it appears that slightly more effective results may be 
expected from late summer or mid-autumn treatment than earlier 
in the season. This is perhaps due in part to the fact that most 
Fig 1 . 10. Showing behavior of the flower heads on a plant in open lawn. 
The bloom is produced quite close to the ground with closed heads bent as low 
as possible during seed-ripening. In the fruiting stage the heads are lifted 
up by the straightening and lengthening of the flower stalk 
of the young seedlings which start in the early summer can be 
killed by the later spraying and that the plants which do survive 
the treatment are much weakened too late in the season for com¬ 
plete recovery before going into the winter. 
As to the number of applications, it is evident from all the 
tests here that at least three sprayings, properly performed, are 
necessary to eradicate the plant. Two thorough sprayings in au¬ 
tumn will greatly reduce the weed, however, and prevent a large 
