Manganese Sulphate upon the Growth of Barley . 581 
Two points stand out clearly from this set of results :— 
(1) The higher concentrations of manganese sulphate have a decided 
retarding effect upon the ripening of the grain. 
(2) While strong solutions of manganese sulphate exert a toxic influence 
upon the growth of barley, very dilute solutions have a definite stimulative 
effect. 
A later series of tests was carried out with pedigree ‘ Plumage ' Barley, 
with the seeds graded to 0-05 and 0*07 gram, in which the plants were only 
Total. 
Shoot. 
Root. 
234 3 6789 1 
Curve 4. Showing the mean value of the dry weights of ten series of barley plants grown with 
manganese sulphate and nutrient salts. 
2. 
1 : 10,000 M.S. 
7 * 
1 :50,000,000 M.S. 
3 - 
1 : 100,000 ,, 
8. 
1 :100,000,000 ,, 
4 - 
1 : 1,000,000 „ 
9 * 
1 :1,000,000,000 ,, 
Control—distilled water. 
5 - 
6. 
1 : 5,000,000 „ 
1 :10,000,000 ,, 
1. 
grown for a limited period, not being allowed to reach the flowering stage. 
In these tests the normal food solution was used (see copper sulphate 
experiments) at about double the concentration of the early manganese sets. 
Five weeks from the start the ‘ browning ' of the roots and discoloration 
of the lower leaves with 1 :10,000 M.S. was manifest, and also at this date 
it was evident that all strengths of solution from 1: 100,000 M.S. downwards 
were supporting plants which appeared better than the controls. This 
phenomenon was consistent through ten similar sets, and continued up to 
