the Broad Bean and certain other Plants. 631 
of the subject, since the reaction of the plant is seen to depend on the crop, 
the nature of the soil, the type of boron compound and the method of its 
application. In addition, the rainfall and other seasonal conditions are 
of the greatest importance. Though the injurious effect of boron on plants 
has been emphasized by the American work, cases of possible stimulation 
are mentioned. However, there is nothing comparable to the extraordinary 
beneficial results obtained by the earlier French work of Bertrand (4 (b)) and 
Agulhon (1 (a )); recently Bruno ( 13 ) has put forward a criticism of the 
methods employed in the U.S.A. as a possible explanation of the inconsis¬ 
tent results obtained in the two countries. But since so little is at present 
known about the part played by such substances as boron compounds in 
the plant, and further the reaction of the plant is dependent on so many 
external factors, it is hardly surprising that all experimental results should 
not fall into line. 
In some experiments carried out by Dr. J. Davidson at Rothamsted in 
1920 in connexion with the bean aphis, broad bean plants in water-culture 
solution supplied with a small quantity of boric acid were strikingly 
superior to the rest of the series. Accordingly, the present investigation 
was undertaken in order to determine more fully the action of boric acid on 
the broad bean and certain other plants. 
II. Experimental Work. 
The methods employed were as follows: 
(1) Water culture. 
(2) Pot culture. 
(3) Field experiments. 
1. Water Cultures. 
Experiments were carried out chiefly with broad beans and barley. 
Germination was effected in damp sawdust, the seedlings being placed 
in their respective solutions when they had developed roots of 1 to 2 in. in 
length, usually about ten days after sowing. 
The Rothamsted food solution, with composition as follows, was used in 
every case : 
kno 3 
1 grm. 
kh 2 po 4 
°‘o » 
NaCl 
°'5 » 
CaS 0 4 
o -5 » 
MgS 0 4 
o -5 » 
FeCL 
0 
0-04 grm. 
' Distilled water to make up 1 litre. 
This solution was tested for the presence of boron, but the result was 
negative. 
