Apr. i6 t 1917 
Absorption of Nutrients 
81 
Phosphorus could not be determined accurately in roots which had 
grown in complete solutions, because of an adhering precipitate of ferric 
phosphate. Hence, in calculating the amount of phosphorus absorbed 
by the plants, account could be taken only of that present in the tops; 
the absolute figures for “grams of phosphorus pentoxid (P 2 0 6 ) absorbed 
per 16 plants” and “grams of phosphorus pentoxid (P 2 0 6 ) absorbed per 
gram of roots,” in this and the following experiment, are thus consider¬ 
ably below the true values. The relative absorption for the different lots 
of plants is pretty well expressed by these figures, however, as the amount 
of phosphorus in the roots ought to be in fairly constant proportion to the 
amount in the tops, except that in plants 17 to 48 it is probably a little 
less than in 49 to 80, as plants 17 to 48 have some roots in the phosphorus- 
free solution. 
If plants 49 to 64 are regarded as normal in growth and phosphorus 
content, it is evident that the partial-phosphorus plants, 17 to 32, made 
the same growth of tops as the normal plants, had 22 per cent greater 
ratio of roots to tops, absorbed 0.76 of the normal amount of phosphorus, 
and absorbed 1.28 times as much phosphorus per gram of roots as the 
normal plants. 
Doubling the phosphates in the solution had about the same effect on 
the plants as doubling the nitrogen in Experiment III. When all the 
roots were in the complete solution, doubling the phosphates in the solu¬ 
tion did not appreciably affect the growth of tops, the ratio of roots to 
tops, the amount of phosphorus absorbed, or the amount of phosphorus 
absorbed per gram of roots. In the case of plants with half their roots 
in the complete solution, doubling the phosphates in the solution had the 
effect of decreasing the ratio of roots to tops, very slightly increasing the 
amount of phosphorus absorbed, and increasing the amount of phos¬ 
phorus absorbed per gram of roots. 
EXPERIMENT VI.—RICE WITH TWO-THIRDS THE ROOTS IN PHOSPHORUS- 
FREE SOLUTION 
To observe the effect of further decreasing the number of roots in the 
complete solution, a test was conducted in which one-third of the roots 
were maintained in the complete solution and two-thirds in the phos¬ 
phorus-free solution. 
The complete acid solution and the phosphorus-free solution were used, 
with ferric tartrate as the source of iron. The number of flasks per unit 
was the same as in the preceding test. The no-phosphate plants were 
grown in 200-c. c. flasks for 40 days; all others, in 200-c. c. flasks for 24 
days and 500-c. c. flasks for 16 days. The solutions were changed nine 
times during the experiment. Experimental data are given in Tables 
XII and XIII. 
