17, 6 
Trelease: Salt Requirements of Wheat Plants 
587 
Concentration, atmospheres. 
0 0.5 t.O 1.6 2.5 3.5 4.5 5.5 7.0 
Fig. 11. Graphs of average total amounts of water absorption for series IV. 
Water requirement. — The data of the amounts of water ab- 
sorbed per unit of dry top and dry root yields are shown in Table 
16. These data are plotted as graphs in fig. 12, where the 
method of plotting is similar to that heretofore employed for 
this series. 
DISCUSSION OF SERIES IV 
Appearance of plants. — In this incomplete series bearing on 
the relation of total concentration to the growth of the plants (it 
being remembered that only three of the many possible sets of 
salt proportions were tested) there was evidence again that the 
occurrence of magnesium injury is generally accompanied by a 
more-intense green color of the foliage. With the set of salt 
proportions producing greatest injury in a concentration cor- 
responding to 1.60 atmospheres of osmotic pressure (T1R1C1), 
the severity of the injury as well as the number of leaves injured 
increased with higher total concentrations and decreased with 
lower. When salt proportions were employed that gave the 
highest dry weight with an osmotic value of 1.60 atmospheres 
(T2R4C2) — which did produce some magnesium injury in series 
I — n o magnesium injury occurred with concentration values 
below 2.50 atmospheres, though such injury did occur with higher 
concentration values. The fact that aerial conditions were dif- 
ferent from those present for series I may possibly explain why 
