630 Warington.—The Effect of Boric Acui and Borax on 
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( e ) Pisum sativum , (1) Harbinger, (2) Pioneer ....... 652 
if) Winter Vetch . . . . • • • • • * • • ^53 
(g) Rye. 
2. Pot Cultures ...... •••-••••• ”53 
A. Broad Beans. ^53 
a. The effect of adding various quantities of boric acid to the soil..... 653 
(a) Boric acid mixed throughout the soil . . . . • • • *654 
(l>) Boric acid supplied as a top-dressing ........ 655 
/ 3 . Comparison between the effect of boric acid and borax in the soil . . • * • 655 
7. Comparison between the application of boric acid at two different stages of growth : 
(1) At the time of sowing, (2) Seventeen days later.657 
B. Barley.65S 
a. The effect of adding various quantities of boric acid to the soil .... 658 
(a) Boric acid mixed throughout the soil ........ 658 
( 3 ) Boric acid applied as a top-dressing fifteen days after sowing .... 660 
/ 3 . Comparison between the effect of boric acid and borax in the soil . . . .661 
3. Field Experiments.665 
A. Broad Beans .............. 665 
B. Barley ............... 665 
III. General Discussion and Summary.665 
IV. Bibliography.670 
I. Introduction. 
T HE action on plant life of chemical elements, other than those usually 
considered nutritive, is of such fundamental importance that a large 
volume of work has been done on the subject. Many of these substances 
have been found to occur naturally in plant tissues, boron being first dis¬ 
covered by Wittstein and Apoiger ( 37 ) in 1857, and since that date many 
investigations have been made on the distribution of boron compounds and 
their influence on plant life. 
Bertrand (4 ( b)) has made a wide study of these plant poisons, including 
boric acid, and has drawn special attention to their beneficial effect when 
presented in very small quantities : Pellet ( 29 ), however, holds that no 
favourable action results from the use of manganese, aluminium, or boron 
compounds in the cultivation of sugar beet ; but Agulhorfs work with 
boron compounds is of particular interest, on account of his exhaustive 
treatment of the subject, and the large variety of plants studied. Most of 
the other important work prior to 1914 has been dealt with by Brench- 
ley(nw). 
More recent investigations have been chiefly American, dealing mainly 
with the toxic effect of boron compounds present in fertilizers used in the 
field. Experiments of this type have been carried out by Conner and Fergus 
( 14 , 15 ), Schreiner and his collaborators ( 33 ), Plummer and Wolff ( 30 ), Proulx 
and others ( 31 ), Brown ( 12 ), Blair (6), and Blackwell and Collins (8). 
The results of these large-scale experiments show clearly the complexity 
