Zinc , Arsenic , Boron on the Growth of Plants. 285 
immediately, as for two or three weeks the shoot growth is apparently 
normal, though the roots are somewhat short and stout, with numerous 
1 = 1:1,000,000 
Curve i. Showing the mean values of the dry weights of fifteen series of barley plants 
(‘Pedigree Plumage’) grown in the presence of anhydrous zinc suphate and nutrient salts. 
(March y-April 16, 1910.) 
stubby laterals. After about a month, however, the shoots appear small 
and weak, and by the time the experiments close, after a growing period 
of six to ten weeks, the shoots are quite dead. Higher concentrations, as 
am. 
1 = 1: 1,000,000 
Curve 2. Showing the mean values of the dry weights of ten series of barley plants (‘ English 
Archer’) grown in the presence of anhydrous zinc sulphate and nutrient salts. (March 2- 
May 8, 1911.) 
1/5,000, kill the plants at an earlier stage of development. As the strength 
of the zinc sulphate decreases, the growth of barley, both as regards the 
shoot and root development, steadily improves, the dry weights showing 
a regular upward curve. As a general rule 1/50,000 zinc sulphate allows 
