640 Waring to n.—The Effect of Boric Acid and Borax on 
the main shoot, though the lower leaves remained yellow and unhealthy. 
In two of these cases a new supply of flowers was produced at the apex, 
although the former ones had withered before maturing and had fallen off. 
It seems probable, therefore, that as these striking recoveries were of such 
universal occurrence throughout the experiment, the assumption that the 
addition of boric acid was responsible for the renewed growth was 
justifiable. 
(/;) Effect of the concentration of boric acid supplied. On the whole 
there was but little difference noticed between the plants treated with the 
July 26, 1922. 
B. Grown with boric acid for different periods ; 1 : 50,000 then removed. Aug. 9- 
Oct. 18, 1922. 
* 
larger and smaller quantity of H 3 B 0 3 respectively. However, there was 
one distinct exception, viz. the set of plants grown for thirty days before 
treatment with boron. In this case those receiving i : 2,500,000 H 3 B 0 3 
were clearly poorer than the corresponding set treated with 1 : 50,000 H 3 B 0 3 ; 
‘ dying off’ was also more prevalent among the former. It seems probable 
that at this time, and under these conditions, a critical stage in the growth 
of the plants had been reached owing to the deficiency of boron, and that 
consequently the plants were particularly sensitive to its action. The 
application of a large quantity would naturally remedy the deficiency 
more rapidly, and possibly even prevent the appearance of the withering; 
a small application, however, such as 1 : 2.500,000, though eventually able to 
