62 



Journal of Agricultural Research voi. xvni. no. 2 



1 91 6 experiment and of magnesium in both experiments at this same 

 stage of growth is so small as to be within the experimental error of the 



36- 



ZA- 



12- 



HEADS 



TOTAL 



WATER 



DRY MATTER 



-a— 



Fig. 5. — Relation of growth of barley to absorption of potassitim, nitrogen, phosphate, calcium, and 

 magnesium, for stems and leaves. To emphasize the comparative diflerences in absorption of these 

 elements, the quantities actually found have been multiplied by 250. Experiment of 1916. 



determination. It is quite possible, however, that the same causes 

 that bring about such substantial losses of potassium and nitrogen at 

 this time and appear to affect 

 calcium, which has such different 

 functions in plant metabolism, may 

 not be without effect on the other 

 elements. When the absolute 

 losses noted above were first ob- 

 served in 1 91 6, we were inclined to 

 doubt the accuracy of our data; 

 but the 1 91 7 experiment confirmed 

 the observation in a most striking 

 and convincing manner. 



Losses OF SOIIv CONSTITUENTS 



FROM The plant. — The losses ob- 

 served were not mechanical losses in 

 decayed leaves (7), since they oc- 

 curred at a period before there was 

 any considerable drying out of the 

 plant ; furthermore the losses of fragments of vegetative tissue were negligi- 

 ble at all times under the conditions of the experiments. Losses from leach- 



FiG. 6. — Relation of growth of barley to absorp- 

 tion of potassium, nitrogen, phosphate, calcium, 

 and magnesium, for heads. To emphasize the 

 comparative differences in absorption of these 

 elements, the quantities actually found have 

 been multiplied by 250. Experiment of 1916. 



