The Dandeeion in Coeorado 
19 
an application of a 12-percent iron sulphate solution on Septem¬ 
ber 16, and an 8-percent solution applied October 10. 
This plat, when inspected May 15, 1917, showed a decrease 
of 36 per cent in the number of plants at first present, while those 
left were weak and small with only about 10 percent able to pro¬ 
duce a few under-sized flower heads. Apparently about 25 per¬ 
cent or 30 percent of young seedling plants had grown up and ap¬ 
peared in the last count. The results of this work compare favor¬ 
ably with that in 1915, Plat III, considering the weaker spray used 
in this case. Considerable injury to the grass resulted from the 
first application, which appears to have been due in part to the 
rather dry condition of the ground in this plat. Similar results 
have been noted under such conditions, in other cases. By June 
1, 1917, the grass had entirely recovered on this plat. 
GENERAL OBSERVATIONS 
Spraying .—Weed control by means of chemicals, known as 
herbicides, has been practiced for a long time both in Europe and 
in this country. The chemicals that have been experimented with 
and employed for this purpose include common salt, copper sul¬ 
phate or blue vitriol, iron sulphate or copperas, sodium nitrate, 
sodium arsenate, ammonium sulphate, potassium chloride, potas¬ 
sium sulphide, slaked lime, corrosive sublimate, carbolic acid, for¬ 
maldehyde, coal tar creosote, gasoline and kerosene, or coal oil. 
While many of these are effective in killing weeds they are also 
destructive to other vegetation as well and are therefore unsuited 
for use on lawns or in fields where crops are grown. 
A suitable herbicide to be used as a spray for eradicating 
weeds in lawns must be capable of killing the weedy plants with¬ 
out serious injury to the lawn grass. In the case of the dandelion, 
sulphate of iron or copperas has been found to be the most useful 
and practicable selective herbicide. Iron sulphate, unlike com¬ 
mon salt, is not apt to produce an injurious cumulative effect upon 
the soil as the chemical becomes oxidized and combined with cer¬ 
tain common constituents of our soils and is thereby rendered in¬ 
soluble and inert. In fact the application of iron sulphate seems 
to stimulate a healthy growth of the grass, after its immediate ef¬ 
fects are passed, so that the lawn appears of a darker green than 
before. 
Strength of Solution .—Most of the work done elsewhere, espe¬ 
cially in the spraying of grain fields for the control of wild mus¬ 
tard, has been done with a solution made by dissolving 100 pounds 
of the granular iron sulphate in a barrel, about 50 gallons, of wa¬ 
ter. Our own experiments seem to indicate that a somewhat weak- 
