INJURY BY DISINFECTANTS TO SEEDS AND ROOTS. 
19 
In another series, in which watering was frequent enough to pre- 
vent injury to most pine seedlings, 0.25 ounce of acid nine days before 
sowing kept the plat free from all w T eeds except three grass plants for 
1£ months, and 0.375 ounce applied at the same time prevented 
weed growth of any sort. While grasses predominated in the un- 
treated plats, they also contained many plants of Mollugo, Portulaca, 
Amaranthus, and Euphorbia, their frequency being in the order 
named. 
In another series watered in the same way, 0.281 ounce of acid 
11 days before sowing and heavier treatments applied to three other 
plats at 'the same time entirely prevented weed growth till 47 days 
afterwards, while the checks contained the same species as those 
in the former series. 
In series 519, plats A, C, and D (Table VI), 0.25 ounce of acid 
had a distinct effect on the weed flora, practically the same as 
0.375 ounce, in plats examined 66 days after application. 
In another series, watered quite frequently after sowing in order to 
prevent acid injury, acid applied 14 days before sowing the pines 
was tested. On adjacent plats the upper 6 inches of soil was par- 
tially sterilized at about the same time by heating in a moist condi- 
tion to above 80° C. in an oven, all parts of the soil being brought 
to at least that temperature and kept there for not less than 10 
minutes. The results are presented in Table IV. 
Table IV. — Weeds which appeared in plats disinfected by heat and by acid. 
Tlat. 
Treatment (ounces 
of acid per square 
foot). 
Weeds found 42 days after treatment. 
None 
60 to 100 per plat; grass commonest, Mollugo and Portulaca fre- 
quent, Amaranthus occasional. 
Grass much as in checks, and making more vigorous growth; 
2 or 3 Portulaca plants, and 1 Amaranthus in each plat. 
5 grass seedlings, with several Mollugo near edge. 
J and K 
Heated 
C 
0.25 
.375 
.375 
.5 
F 
5 grass, with 1 Portulaca and 1 Mollugo near edge. 
G 
D 
3 grass. 
Evidently, unless the grass seed survived a temperature of 80° C. 
or more, it had been blown into plats J and K after treatment, and 
migratory ability may explain part of its predominance over the 
dicotyledons in acid- treated plats. The results in general, neverthe- 
less, indicate that it is somewhat more resistant to acid than the 
dicotyledons. 
RELATION BETWEEN TIME OF APPLICATION AND AMOUNT OF INJURY. 
The foregoing experience with pines and other plants in beds 
treated with acid at the time of germination, at sowing time, and at 
various times before sowing, shows clearly, as would be expected, that 
