Rate of Absorption of Various Salts by Plant Tissue. 493 



The initial rates of absorption indicated are in the order K, Na, Mg, Zn, 

 and this order remains the same at the end of the experiment. 



The figures given in Table IV, compared with those obtained for chlorides, 

 show how much less is the apparent absorption from potassium and sodium 

 sulphates than from the corresponding chlorides. The difference is so great 

 that it can scarcely be referred to differences in the tissue used in the two 

 series. Nevertheless, all the experiments in the sulphate series were 

 repeated, and the same results obtained. A comparative series with anions 

 given later confirmed this result. 



The behaviour of potato in solutions of sulphates is very similar to its 

 behaviour in solutions of chlorides. As before, the apparent initial absorp- 

 tion of the sodium salt is less than that of the potassium salt, but subse- 

 quent exosmosis prevents the obtaining of definite data as to the subsequent 

 course of absorption by potato. The results obtained are shown in Table V, 

 and graphically in fig. 4. They suggest the same order of absorption as with 

 carrot. The order of the coefficients of diffusion of the four sulphates used 

 is K, Na, Zn, Mg, while the order of absorption by carrot and potato is 

 K, Na, Mg, Zn. There is thus a parallelism between the absorption and the 

 coefficient of diffusion, although the position of zinc differs in the two series. 

 It should be noted that the position of zinc in the absorption series is 

 doubtful ; as, on account of secondary changes resulting in exosmosis, more 

 may be absorbed than appears from the observed results. 



Table V. — Potato in Solutions of various Sulphates of Concentration N/50. 



Potassium 

 sulphate. 



Sodium sulphate. 



Magnesium 

 sulphate. 



Zinc sulphate. 



Aluminium 

 sulphate. 



Time 



in 

 hours. 



Change 

 in 



electrical 



con- 

 ductivity. 



Time 



in 

 hours. 



Change 

 in 



electrical 



con- 

 ductivity. 



Time 



in 

 hours. 



Change 



electrical 



con- 

 ductivity. 



Time 



in 

 hours. 



Change 

 in 



electrical 



con- 

 ductivity. 



Time 



in 

 hours. 



Change 

 in 



electrical 



con- 

 ductivity. 



0- 5 



1- 12 

 14 -0 

 20 -0 

 41 -75 



- 91 



- 91 



- 25 

 + 64 

 + 225 



0- 5 



1- 13 

 14 -0 

 20 -0 

 41 -75 



- 79 



- 59 

 + 31 

 + 101 

 + 345 



0-5 



13-85 

 19 -87 

 41 -56 



- 3 



+ 101 

 + 184 

 + 336 



0-5 



14-3 

 19 -51 

 41 -28 



+ 15 



+ 142 

 + 170 

 + 506 



0-5 



13-78 

 19-28 

 41 -28 



+ 55 



+ 200 

 + 248 

 + 643 



3. Nitrates. — The nitrates of potassium, sodium, calcium, aluminium, and 

 zinc were employed. The initial apparent absorption by carrot is very 

 marked with potassium and sodium nitrates, less so with calcium and zinc 

 nitrates, and slight but yet distinct with aluminium nitrate. With zinc 



