the Broad Bean and certain other Plants. 
657 
treated sets was seen, for in the former case only were the roots well developed 
near the surface, though as regards total length the two cases were very 
similar. This is quite in accordance with what might be expected, for the 
roots in the heavily treated pots would natually make most growth in 
the less toxic region, i. e. other than the surface soil which had received the 
dressing. A similar result has been described by Breckenridge (10), but 
as he applied the borax below the seed, the roots developed mainly at the 
surface, which was in this case the less toxic soil layer. 
y. Comparison between the Application of Boric Acid at tzvo Different 
Stages of Growth. 
In the preliminary experiment a (b) the dressing was applied some 
time after sowing, but in the succeeding case J 3 the soil was treated before 
germination had taken place. 
Since the time of application of manurial dressings is of such impor¬ 
tance in agricultural practice, a series of pots were set up to ascertain if there 
Table VI. 
Mean Green and Dry Weights of Broad Beans grown in Pot Cidtnre. 
Average of 5 or 6 pots. 2 plants per pot} 
Mar. \-May 31, 
1921. 
April 15 -June 29, 
1921. 
July \-Sept. 23, 
1922. 
Mixed throughout Top-dressed 2 5 days Top-dressed directly 
the soil. after sowing. after sowing. 
17 days later. 
IhBO 3 
per pot. 
Green IVt. 
Dry IVt. 
Green IVt. 
Dry IVt. 
Green IVt. 
Dry IVt. 
Green IVt. 
Dry IVt. 
grm. 
grm. 
grm. 
grm. 
grm. 
grm. 
grm. 
grm. 
grm. 
4-0 
41-10 
6.20 
0-0 
0-0 
— 
— 
— 
— 
2.0 
74 -io 
11 -69 
0-0 
0-0 
— 
— 
— 
— 
1-0 
122.37 
18.49 
0-0 
C.o 
— 
— 
— 
—- 
o *5 
143-35 
22.03 
65-32 
11.92 
125.18 
1 5 -S 1 
H 7-54 
x 4’93 
0.1 
135-63 
21-16 
118.84 
21.76 
152.56 
20.70 
114-85 
19.60 
0-02 
128-05 
19-70 
122.32 
21.88 
155 - 8.3 
20*59 
160-36 
21.23 
Control 
125-34 
21-33 
114.58 
20.95 
i 5 9 -i6 
21-28 
159.16 
21-28 
was any 
difference in the effect 
of the 
boric acid dressing when 
added 
immediately after sowing or when the plants were several inches high, both 
sets of plants being grown under strictly comparable conditions. 2 
Accordingly 0*5 grm., o-i grm., and 0-02 grm. H 3 B 0 3 per pot was 
applied as a top-dressing— 
(1) At the time of sowing. 
(2) Seventeen days later. 
In the first case, toxic effects such as retardation of germination and 
leaf injury were noticeable where 0*5 grm. H 3 B 0 3 had been applied, and even 
o-j grm. proved slightly unfavourable (Table VI). Where the dressing was 
1 Pots containing only single plants were omitted in the mean. 
2 Infestation with aphis was successfully checked by spraying with 0.15-0-2 per cent, nicotine in 
soap solution of 1 oz. per gallon. This had no apparent effect on experimental results. 
X X 2 
