656 Warington.—The Effect of Boric Acid and Borax on 
boric acid, equivalent amounts of boron being supplied in each case (i*o 
boric acid = 1*54 borax). The top-dressings were applied at the time of 
sowing. 
1 grm. H 3 B 0 3 was the heaviest dressing given in this experiment, as 
any larger quantity was strongly toxic. Germination was decidedly 
retarded and the plants were yellowish green with brown-edged leaves. 
The corresponding borax set were also very poor plants, though they 
apparently suffered rather less injury than those treated with the equivalent 
quantity of boric acid. Some indication of the more poisonous nature of 
H 3 B 0 3 is evident from the green weight value, but no contrast is shown in 
the dry weights (Table VI). 
Haselhoff (20) found that borax is less injurious to Phaseolus vidgaris 
in soil culture than a similar quantity of boric acid, but in the present case 
an even larger amount has proved less toxic. 
0-5 grm. boric acid per pot was again slightly more toxic than the 
corresponding amount of borax, but the injury in both cases was much less 
severe than where the heavier dressings had been supplied. Still lower 
quantities of boric acid or borax caused no toxic effect at all, the drop in 
the green and dry weight of the borax set being most likely due to indi¬ 
vidual variation (Table VII). However, no beneficial effect was apparent 
either, both sets of plants closely resembling the controls in colour, height, 
general appearance, and green and dry weight. 
The difference in the degree of injury caused by a dressing of 1 grm. 
boric acid in this case and the previous experiment seems to require some 
explanation (Tables VI and VII). The boric acid was applied at different 
stages in the growth of the plant in the two cases, but a subsequent experi¬ 
ment has shown that under similar conditions no great difference, at least in 
the dry weight, results from* an alteration in the time of application. The 
great contrast in the seasons 1921 and 1922 more probably accounts for the 
discrepancy between the results. From this it seems probable that, though 
borax may be slightly less toxic, there is little if any real differerence 
between the action of borax and boric acid ; which points to the fact that 
the element boron is the important factor in both cases, as Peligot ( 28 ) 
showed in 1876. 
In order to determine whether these dressings had any marked effect 
on the root system as well as on 4 the shoot, several roots were washed out 
from the soil, typical plants being chosen. It was found that in the case of 
plants treated with either 1 grm. of H 3 B 0 3 or the corresponding quantity 
of borax, the roots were long and not at all plentiful, being especially scarce 
in the surface layers, but tubercle formation was apparently normal. On 
the other hand, plants receiving a small dose of H 3 B 0 3 , e. g. 01 grm., had 
a large root system similar to the untreated plants. A striking contrast 
between the root growth of the control plants and that of the heavily 
