17, 6 Trelease: Salt Requirements of Wheat Plants 547 
The interpolated values thus obtained for M, are inserted in 
roman type in the third column of the same table, and each of 
these is taken as the volume-molecular concentration of potassium 
chloride required to produce the corresponding partial osmotic 
pressure given in the second column. It will be seen that only 
these interpolated values were actually employed in making up 
the solutions. These are the values given in the second column 
of Table 2. Cs olay 
Similar calculations were made for each of the other three 
salts. The degrees of dissociation for calcium nitrate and mag- 
nesium sulphate were taken from Noyes and Falk, while those 
for monopotassium phosphate were obtained from Abbott and 
Bray.*® The data used in making the calculations for these 
three salts will not be given here, but the final interpolated values 
are given in the last three columns of Table 2. 
Many of the solutions used in this set were subjected to freez- 
ing-point determinations by the Beckmann method, in the same 
way that Shive ** tested the total concentrations of Tottingham’s 
and his own solutions. It was found that the lowering of the 
freezing point (A) for the solutions of this series varied from 
about 0.11° to 0.13°. Calculating the osmotic values correspond- 
ing to these limits, it appears that these values (for 25° C.) 
varied from about 1.50 to about 1.70 atmospheres.*? The error 
in the osmotic value here introduced may be considered as 
negligible in this kind of work, for it will be recalled that 
those solutions were calculated to have an osmotic value of 1.60 
atmospheres. 
RESULTS OF SERIES I 
Appearance of plants.—During the early part of the twenty- 
four-day period of series I most of the cultures were alike in 
appearance, although root development was noticeably retarded 
in some of the cultures as early as the time of the first renewal 
of solution. These injured cultures were the ones in solutions 
“ Abbott, G. A., and Bray, W. C., The ionization relations of ortho- and 
Pyrophosphoric acids and their sodium salts, Journ. Am. Chem. Soc. 31 
(1909) 729-768. 
“Shive, J. W., The freezing points of Tottingham’s nutrient solutions, 
Plant World 17 (1914) 345-353. Also, see Shive, J. W., Am. Journ, Bot. 
2 (1915) 157-160. 
“The following approximate formula was used for this calculation: 
298 
« 26° = 273 12.06 A = 13.164 A. 
