672 Warington.—Effect of Boric Acid and Borax on the Bean. 
EXPLANATION OF PLATE XIII. 
Illustrating Miss Warington’s paper on the Effect of Boric Acid and Borax on the Broad Bean 
and certain other Plants. 
All plants have been grown in water culture in nutrient solution. 
Photograph 1. Typical root of broad bean grown without boric acid. 
Photograph 2. Typical root of broad bean grown with a small quantity of boric acid. 
Photograph 3. Broad bean shoot showing new growth (on left) subsequent to the addition of 
boric acid after the characteristic death of the main axis (on right). 
Photograph 4. Broad bean showing the comparative size of shoots before and after the addition of 
boric acid. The small main axis (on left) was the only shoot before treatment with boric acid. 
Photograph 5. Broad beans grown with various concentrations of boric acid ; (left to right) 
I : 5,000 ; I : 50,000 ; 1 :100,000 ; 1 : 500,000 ; control with no boric acid. 
Photograph 6. Addition of boric acid to broad beans after increasing periods before treat¬ 
ment; (left to right) o, 10, 20-60 days. 
Photograph 7. Removal of boric acid from broad beans after increasing periods of treatment; 
(left to right) o, 10, 20-70 days. 
Photograph 8. Barley grown with various concentrations of borax; (left to right) control with 
no borax; 1 : 100,000,000 increasing to 1 : 50,000 (terms given as boric acid). 
Photograph 9. Comparison between barley grown with boric acid (1 : 12,500,000) and borax (on 
right) containing equivalent boron. 
Photograph 10. Preliminary result of the effect of boric acid on the runner bean. Control with 
no boric acid (on left); 1 : 2,500,000 (on right). 
Note.— Since this paper went to press attention has been drawn to 
a paper by Addoms (Amer. Journ. Bot., x, 1923) in which the author shows 
that a short, stubby, branched root system (as described above on p. 634) is 
associated with high concentrations of potassium di-hydrogen phosphate 
and the consequent high hydrogen-ion concentration. However, although 
the nutritive solution used in these experiments contained a relatively large 
amount of this salt, yet it is not entirely responsible for the distinctive root 
growth here described, as a very similar type of root system has since been 
obtained when part of the phosphate was supplied in the form of the 
mono-hydrogen salt, thereby considerably reducing the hydrogen-ion con¬ 
centration. 
