damping-off in forest nurseries. 25 
would presumably kill all seedlings on the area treated, but would, 
of course, be of considerable value in stopping at the outset such 
mycelia as those which caused the damped-off area in figure 7. The 
procedure would be of practical value only in cases in which damp- 
ing-off was chiefly limited to a few large patches of this sort, a rather 
rare condition in conifers. 
Copper sulphate solutions have been used on pine seed beds at the 
time of sowing with considerable success at some nurseries (65, 67). 
Except in a nursery in which the soil contained carbonates, it has 
proved rather difficult to prevent injury to the pines. The trial of 
some such combination of copper sulphate and lime as was used 
by Spaulding (136) on the surface of pine beds before sowing, which 
apparently prevented the damping-off of lettuce in some unpub- 
lished pot experiments of Mr. J. F. Breazeale, is considered desir- 
able. Treating seed beds with ordinary Bordeaux mixture has also 
been recommended. Home (78) secured especially good results 
against Corticium vagum in tobacco seed beds by heavy applications 
of Bordeaux mixture, and Schramm (122) and Clinton (28) have 
obtained indications of its value as a spray in preventing the damp- 
ing-off of conifers. It is probably worth further tests in various 
amounts of application. In tests conducted by the writer in 1912 
and still unpublished, some advantage was indicated for Bordeaux 
mixture as a surface treatment after soil disinfection with acid. 
Zinc chlorid as a soil disinfectant has also been found valuable in a 
number of cases (65, 67), but it is more expensive and apparently less 
dependable than copper sulphate. 
Formaldehyde and sulphuric acid have been tested more fre- 
quently than other disinfectants. The use of sulphuric acid on 
coniferous seed beds was originated by Spaulding (136). The first 
intensive experiments with this acid were reported by the writer (63) . 
The first experiments with formaldehyde on conifers seem to have 
been in the early greenhouse tests of Spaulding (137), repeated in 
forest nurseries in 1907 by Jones (83) and Spaulding (136). Most 
of the experiments with these two substances have already been sum- 
marized (67). A report not mentioned in this summary is that of 
Schaaf (119, p. 88), who obtained favorable results with the acid. 
The great trouble with formaldehyde is its tendency to kill dormant 
seed. The length of time which must be allowed to elapse between 
treatment and sowing in order to avoid this killing varies with con- 
ditions. Formaldehyde is more expensive than acid and seems on 
the whole to have been less effective in disease control. Acid, on the 
other hand (applied just after the seed is sown, which is found to be 
the best time) , on a few soils has caused injury to radicles, which it was 
at first thought could be prevented only by very frequent watering 
during the germination period; while in a few cases, when cold 
