14 
BULLETIN 934, U. S. DEPARTMENT OF AGRICULTURE. 
cases. It may furthermore be that in other cases the disinfectant had 
a stimulating effect, resulting in better germination in the treated 
plats, entirely aside from that resulting from parasite control. The 
number of disinfectant methods which concurred in giving apparent 
increases in germination, however, makes it seem reasonably cer- 
tain that no great part of the increase was due to this stimulation. 
In addition to the different disinfectants shown in the table, mer- 
curic chlorid, heat, hydrochloric acid, nitric acid, and ammonia all 
apparently resulted in approximately the same increases of germina- 
tion in tests at the Bessey Nursery as the sulphuric acid which was 
used as the standard for comparison in most of the series. Relative 
emergence in treated and untreated plats, as well as damping-off 
Fig. 7. — A . clean-killed area in a bed of Pinus ponderosa, caused by Cortioium vagum. 
Inside a 12-inch circle at the center of this " patch " no seedlings appeared. It will 
be noted that the weeds as well as the pines have been killed with the exception of 
Salsola tragus. 
loss after the seedlings appeared, was determined at two nurseries 
in addition to those given in the table. The results at these nurseries 
in general confirmed those at the five nurseries covered by the 
table in showing lower emergence in the controls. Although it is 
impossible to draw positive conclusions, some idea of the seriousness 
of losses before the appearance of the seedlings above ground can be 
obtained by studying the data in Table I. The fact that such losses 
appear considerable, sometimes exceeding the losses from the damp- 
ing-off that occurs after emergence, is believed to explain the com- 
mon failure to secure satisfactory results from control measures 
taken after the seedlings have come up and the disease has become 
noticeable. It is somewhat interesting to note that the data in the 
