16,5 Espino: Salt Requirements of Young Rice Plants 469 
THE STOCK CULTURE SOLUTIONS 
Three types of nutrient solution were studied: 
(1) The 3-salt type studied by Shive (1915, 1917) with wheat ‘and 
buckwheat,” which has been called the 3-salt type I by Livingston 
and Tottingham.” This contains, besides a small amount of ferric 
phosphate, the three salts monopotassium phosphate, calcium ni- 
trate, and magnesium sulphate. 
(2) A 4-salt type with both ammonium and nitrate. This contains, 
besides ferric phosphate, the four salts monopotassium phosphate, 
calcium nitrate, magnesium sulphate, and ammonium sulphate. 
It will be termed the 4-salt type A. 
(3) A 4-salt type with ammonium but without nitrate. This contains, 
besides ferric phosphate, the four salts monopotassium phosphate, 
monocalcium phosphate, magnesium sulphate, and ammonium 
sulphate. It will be termed the 4-salt type B. 
For each of these three types stock culture solutions were 
prepared from the requisite single-salt stock solutions and dis- 
tilled water, the total concentrations of the stock culture solu- 
tions of each type being alike and as high as that used for the 
Most concentrated culture solution. No ferric phosphate was 
added to the stock culture solutions. For each type there were 
aS Many of these stock solutions as there were different sets 
of salt proportions in the list to be tested. From any given 
Stock culture solution the various total concentrations needed 
for the cultures employing that particular set of salt propor- 
tions could be readily obtained, either directly or by simple 
dilution. These concentrated stock culture solutions were stored 
in much-used glass bottles (of about 3.5 liters’ capacity), practi- 
cally in darkness, and they were drawn upon from time to time 
as the culture solutions were renewed. In the case of the 3-salt 
type these stock culture solutions were kept for about a month; 
im the case of the two 4-salt types they were kept twice as 
long. In no case was there any evidence suggesting alteration 
m the stock solutions; at least none beyond the occasional ap- 
pearance of small fungus colonies, which were always removed 
with a glass tube as soon as they became conspicuous. 
The employment of concentrated stock culture solutions from 
Which the actual culture solutions were obtained, by simple di- 
lution—a procedure that saves very much time, tends to,sim- 
plify the culture work, and avoids the possibility of many errors 
_ _ Shive, John W., A study of physiological balance of buckwheat grown 
Mm three-salt solutions, New Jersey Agr. Exp. Sta. Bull. 319 (1917) 5-63. 
™ Livingston, B. E., and Tottingham, Wm. E., A new three-salt nutrient 
Solution for plant culture, Am. Journ. Bot. 5 (1918) 337-346. 
