26 BULLETIN 934, IT. S. DEPARTMENT OE AGRICULTURE. 
weather resulted in a long germination period, it has killed or in- 
hibited the germination of some of the dormant seed. All injury 
can be prevented by treatment a few days before sowing, followed 
by the addition of lime just before sowing, but lime used in this 
way has apparently destroyed a considerable part of the value of the 
acid treatment against the disease. Further consideration of the 
data on which earlier papers (63, 67) were based indicates that the 
apparent need for frequent watering during the germination period, 
which was required at a few of the nurseries where the first tests of 
acid treatment were made, as well as practically all of the germina- 
tion reduction, was due to the use of unnecessarily large applications 
of acid and that the trouble can be eliminated by determining by 
test the minimum quantity of acid which will be reasonably effective 
in each locality. If this can be done it should establish the acid 
treatment as the most profitable for general use of any of the 
methods of damping-off control which have so far been extensively 
tested. 
In view of the various parasites which may cause damping-off at 
different times and places and which vary greatly both in their 
means of dissemination and in their physiological qualities, it is not 
believed that any single disinfectant will be found entirely satisfac- 
tory at all nurseries. It is also unfortunately true that no one 
strength of treatment can be recommended for all nurseries. The 
quantity of acid to be used at any specified nursen^ will have to be 
determined by test at that nursery. A single test, no matter how 
well conducted, is not sufficient to serve as a basis for conclusions. 
However, a number of small-scale tests, made at different times and 
in different parts of the seed-bed area, should determine the best 
treatment for any particular nursery with a reasonable degree of 
certainty and with very little work. If the plats are equal in size 
and receive equal quantities of seed, all the nurseryman needs to do 
to determine the value of the treatments is to count the number of 
living seedlings on the different plats at the end of the season. The 
decrease in the number of weeds as a result of the use of acid is 
itself sufficient at a number of nurseries to pay the entire cost of the 
treatment. Detailed methods of application have already been pub- 
lished (67). The differing proportions of acid between which the 
best treatment will ordinarily be found to lie are 2 and 7 c. c. (one- 
sixteenth and one-fourth of a fluid ounce) of the concentrated com- 
mercial acid per square foot of seed bed, applied just after the seed is 
sown and covered. It should be dissolved in 500 to 1,000 c. c. (1 to 2 
pints) of water per square foot of bed before applying. The drier 
the soil before treatment, the more water should be used in dissolving 
the acid. 
No treatment applied after germination begins can have the maxi- 
mum value in controlling the disease, because the damping-off para- 
