the Bread Bean and certain other Plants. 
64 I 
bring - about recovery, would conceivably be insufficient to check the ‘ dying 
off’, and the appearance of this phenomenon in several plants can be thus 
accounted for. 
The dry weight values (Table II and Text-fig. 3, a) are in a more or 
less strict downward sequence from those plants which were continuously 
supplied with boric acid to those which were treated for a few days only. 
Allowing for individual variation, the actual concentration of boric acid 
supplied is seen to have had little effect on the dry weight, except in the 
case to which attention has already been drawn, and possibly in this case 
also individual variation may have caused the result to be unduly accen¬ 
tuated. 
Table II. 
Mean Dry Weight of Broad Beans supplied zvith Boric Acid at 
Different Stages of Growth. 
May 21 -July 26, 1922. Average of 5 plants. 
Days 
fol/o 7 oed 
by 
Days 
1 : 
50,000 HoBOr,. 
1 : 2, 
500,000 HnBOn. 
without 
with 
Root. 
Shoot. 
1 otal. 
Root. 
Shoot. 
Total. 
grm. 
grm. 
grm. 
grm. 
grm. 
grm. 
0 
66 
3-94 
16.83 
20.77 
3-32 
14-16 
17.48 
10 
56 
3.18 
14.84 
18-02 
3.22 
L 5 -I 5 
1 8-37 
20 
46 
2*67 
11.18 
13-85 
2-26 
9.41 
11-67 
30 
36 
2.60 
10-40 
13.00 1 
1-28 
4*n 
5 - 39 1 
4 ° 
26 
I-I2 
5-30 
6.42 1 
i-i 5 
5 - 4 2 
6-57 1 
50 
16 
1.16 
4 - 6.5 
5.Si 1 
1-00 
5*°3 
6*03 1 
60 
6 
o-8o 
4 - 65 
5-45 12 
0.51 
2.42 
2 - 93 1 
y. The Effect of removing Boric Acid at Different Stages of Growth. 
On transferring a few plants grown for twenty days in a nutrient solution 
containing 1 : 50,000 H 3 B 0 3 to ordinary culture solution, it was evident 
that a deficiency of boron was felt, as ‘dying off’ set in after about three 
weeks. Accordingly, an experiment was set up to see the result of depriv¬ 
ing plants of boron after being supplied with H 3 B 0 3 for different periods, 
since apparently the boron absorbed in twenty days was inadequate for the 
whole growth period. 
Besides the usual nutrient salts, half the plants were treated with 1150,000 
H 3 BO : , and the other half with 1 : 2,500,000 H 3 B 0 3 . In addition, ten plants 
received no boric acid at all. All the solutions were renewed every ten 
days, five plants hitherto treated with one or other of the two strengths of 
boric acid being placed in ordinary culture solution at each change, and not 
1 Average of three plants only, as the remainder were carried on longer for observations on the 
recovery. 
2 These plants may be regarded as controls, as the application of boric acid had no apparent 
effect during the 6 days. 
U U 2 
