92 Walter Stiles 
while the final order is N 0 3 , Cl, S 0 4 , 
the change again being due to the position of the divalent ion, in 
this case sulphate. 
Fitting (1915) and Trondle (1918 a) have attempted to follow the 
rate of absorption of salt by measuring the rate of deplasmolysis by 
their methods described in the last chapter. Fitting concluded that 
potassium chloride and potassium nitrate penetrate with ease the 
protoplast of the epidermal cells of Rhoeo discolor, but that potassium 
sulphate penetrates much more slowly. Sodium chloride and sodium 
nitrate both penetrate into the cells, whereas lithium chloride and 
lithium nitrate enter much more slowly. Magnesium chloride, nitrate, 
and sulphate only penetrate slowly, while no penetration of calcium 
and barium salts examined could be observed. The order of absorption 
found by Fitting for kations was thus 
[K, Na], Li, Mg, [Ca, Ba], 
and for anions [NO s , Cl], S 0 4 . 
Later, Fitting (1919) examined the permeability of the same and 
other cells to glycerol and urea and concluded that urea was absorbed 
at about the same rate as potassium nitrate or sodium chloride, but 
that glycerol was absorbed much more rapidly. 
Trondle employed the same method in order to determine the 
intake of salts by roots of Lupinus albus and palisade cells of the 
leaves of Acer platanoides and Salix babylonica, and decided that 
kations were absorbed in the order 
Rb, K, Li, Mg, Ba, Sr, Ca, 
and anions in the order N 0 3 , Cl, S 0 4 . 
Kahho (1921 d) investigated the entrance of a number of salts 
into the young roots of the yellow lupin by means of Lundegardh’s 
method of tissue contraction and extension described in the last 
chapter. In order to obtain comparable results with different salts 
isotonic solutions were used, Fitting’s values (1917) of isotonic co¬ 
efficients being accepted. Kahho came to the conclusion that the 
order of absorption of kations is 
K, Na, Li, Mg, [Ca, Ba], 
while the order for anions is 
[Br, I, NO s ], Cl, tartrate, S 0 4 , citrate. 
While all these results agree in the main with those of Stiles and 
Kidd, it is clear from the results obtained by the latter workers that 
the plasmolytic and tissue extension methods cannot be expected 
