460 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
Mayer (7)^ prepared a similar solution, eliminating zinc, iron, and 
silicon, but including calcium acid phosphate in addition to the other 
elements. 
Simpler synthetic solutions were later devised by Pfeffer (11),* Richards 
(13),^ Currie (3),^ Uschinsky (5),"^ and Czapek (4),^ and these are frequently 
used in present-day studies. 
^ MaN^er's synthetic solution: 
Magnesium sulphate 2.5 g. 
Ammonium nitrate 10. o g. 
Calcium phosphate, Ca3(P04)2 2.5 g. 
Potassium acid phosphate (monobasic) 5.0 g. 
Cane sugar 50.0 g. 
Water 1000.0 cc. 
* Pfeffer's solution: 
Ammonium nitrate 10. o g. 
Potassium phosphate (monobasic) 5.0 g. 
Magnesium sulphate 2.5 g. 
Cane sugar 50.0 g. 
Ferrous sulphate trace 
Water ' 1000. cc. 
Reaction, pH = 4.3 
^ Richards' solution: 
Potassium nitrate i. g. 
Potassium acid phosphate (monobasic) 0.5 g. 
Magnesium sulphate 0.25 g. 
Ferric chloride , trace 
Saccharose 343 g- 
Water. . . , 100. cc. 
Reaction, pH 4.2 
^ Currie's solution: 
Ammonium nitrate 2, g. 2.5 g. 
Potassium acid phosphate (monobasic) -75 g- i-O g- 
Magnesium sulphate -25 g. -25 g. 
Cane sugar 125.00 g. 150.00 g. 
Water 1000 cc. 
Reaction (add 4 cc. of AV5 HCl), pH = 34-3.6 
^ Uschinsky's solution: 
Ammonium lactate 6.7 g. 
Sodium asparaginate 3-4. g. 
Potassium acid phosphate (monobasic) 2-2.5 g- 
Magnesium sulphate 0.3-0.4 g. 
Sodium chloride 5-7. g. 
Calcium chloride O-i g- 
Glycerin 30-40. g. 
Water 1000. cc. 
^ Czapek's solution: 
Magnesium sulphate 0.5 g. 
Potassium acid phosphate (monobasic) i-O g. 
Potassium chloride 0.5 g. 
Sodium nitrate 2.0 g. 
Cane sugar 3.4 g. 
Water 100. cc. 
Reaction, pH = 6.8 
