200 The Woburn Pot- Culture Experiments , 1904. 
It was decided to carry on the investigation further in 1904 
as regards the action of manganese salts on wheat and barley, 
and to compare this with that of iron salts. A further experi- 
ment resolved on was the influence of the direct application of 
silicate of potash and silicate of soda to wheat and barley. 
• 
1. ( a ) The Influence of Sulphate of Manganese and 
Sulphate of Iron on Wheat. 
{Jo) The Influence of Silicate of Potash and Silicate of 
Soda on Wheat. 
These two sets of experiment were carried on simultaneously. 
The salts employed in the first set were sulphate of manganese 
and sulphate of iron. These were used in two different ways : 
(1) as solutions of varying strength, in which the seed was 
soaked before planting; (2) as solutions in water directly 
applied at different times to the growing plant. In the second 
set the silicates of potash and soda were mixed at the com- 
mencement with the top 4 lb. of soil in each pot. 
The soil used was that from Stackyard Field, the pots were 
earthenware ones, and each experiment with the manganese 
and iron salts was in triplicate, and with the silicates in dupli- 
cate. “ Grey-chaff Browick ” was the variety of wheat sown. 
The strengths of solutions of sulphate of manganese and 
sulphate of iron for soaking the seed in were 1 per cent., 2 per 
cent., and 5 per cent. ; and of the solutions directly applied, 
such as to supply respectively J cwt., \ cwt., and 1 cwt. per 
acre of the different materials. The applications of silicates 
were equivalent to dressings of 2 cwt. and 4 cwt. per acre, 
respectively. The seeds — twelve per pot — were sown in all 
cases on December 15, 1903, seed soaking, where done, being 
carried out previously to sowing, and the direct application of 
solutions taking place on January 26, 1904 (when the wheat 
plants were 2 in. high), March 31, and April 20. The first 
noticeable point was the influence of the seed-soaking on the 
germination. The germination with the untreated seed was 
80 per cent., and this was increased to 94 per cent, by soaking 
the seed for fifteen minutes in a 1 per cent, solution of sulphate 
of manganese, and to 92 per cent, with a 2 per cent, solution ; but 
a 5 per cent, solution seemed too strong, the germination going 
down to 73 per cent. With sulphate of iron (seed soaking) the 
germination was 88 per cent, with 1 per cent., but reduced to 
75 per cent, with a 2 per cent., and to 63 per cent, with a 5 per 
cent, solution. When the solutions of the manganese and iron 
salts were directly applied to the growing plants, the germina- 
tion (80 per cent, with untreated) was as follows : sulphate 
of manganese, J cwt. per acre, 88 per cent. ; \ cwt., 86 per 
cent. ; 1 cwt., 80 per cent. : sulphate of iron, J cwt. per acre, 
