372 EK. P. Deatrick 
turgor and dry up, and no trace of new rootlets is apparent. In a solution 
containing 1000 parts per million of manganese sulfate, the leaves of 
barley plants faded to yellow and then turned brown. These investi- 
gators found also that barley became chlorotic and the roots turned 
brown in solutions containing only small quantities of manganese. 
McCool (1913) noted that a solution containing 15 parts per million 
of manganese in the form of chloride is injurious to field peas, and that 
a solution containing 30 parts per million prevents root growth entirely. 
Miss Brenchley (1914) found that manganese when present in strong 
concentrations exerts a toxic influence on higher plants. 
On the other hand, several investigators have obtained plant stimulation 
in distilled water cultures containing small quantities of manganese. 
Micheels and De Heen (1906) obtained a pronounced stimulation in 
colloidal solutions of manganese. McCallum (1909) reported an accelera- 
tion of tuber formation when potatoes were treated with a solution of 
manganese chloride. Montemartini (1911), altho finding marked differ- 
ences in the sensitiveness of plants, obtained increased growth with all 
plants used in his experiment. McCool (1913) found slight stimulation, 
as shown by length of the roots of pea seedlings, but the leaves showed 
no effect. 
The effects of manganese in solutions containing nutrient salts are 
similar to those obtained with distilled water cultures, but experiments 
show that the nutrients greatly reduce the toxicity of the manganese. 
McCool (1913) found that this reduction of toxicity is proportional to 
the concentration of the nutrient salts. 
According to Miss Brenchley (1914), 
the Rothamsted experiments supported Aso’s work on the action of manganese sulphate 
on barley, concentrations of the salt above 1/100,000 having a retarding influence on the 
growth, the roots being coloured brown and the leaves also showing discolouration. At an early 
stage in growth the lower leaves of the plants receiving the most poison began to be flecked 
with brown spots. 
A solution containing 1350 parts per million of nutrient salts and 770 
parts per million of manganese in the form of sulfate, reduced the yield 
31 per cent. A solution containing but 0.01 of this amount of manganese 
developed brown roots after four weeks and reduced the yield 3 per cent. 
In lower concentrations manganese was decidedly stimulative. Aso 
(1902-03) found that manganese stimulated the growth of a number of 
plants. The solutions which he used contained 0.5 per cent of nutrient 
