616 Journal of Agricultural Research vol. xx, No. 8 



from analyses to contain potassium, it will be noted that the wheat seed- 

 lings were unable to absorb any of it. This is of special interest, since 

 the avidity of wheat seedlings for potassium is very marked. 



The culture solutions in series b, Table I, included a control of distilled 

 water (No. i), 40 gm. of finely ground orthoclase in 2,500 cc. of distilled 

 water (No. 3), and potassium chlorid solution containing 4 parts per million 

 of potassium oxid (No. 5). Culture solutions Nos. 2, 4, and 6 were similar 

 to No. 1, 3, and 5, respectively, except that gypsum was added to each 

 in excess, so that it would always be present in the solid phase. To each 

 of the six cultures were added also 50 parts per million of nitrate (N0 3 ) as 

 sodium nitrate and 50 parts per million of phosphoric acid (P 2 5 ) as 

 sodium phosphate. Each solution, except those in which orthoclase 

 was present in the solid phase, was changed twice daily in order to insure 

 uniformity in concentration and freedom from bacterial disturbances. 

 The wheat seedlings were grown in these culture solutions for 10 days. 

 The analyses of the plants indicated, as before, that the wheat seedlings 

 were unable to remove potassium from the orthoclase solutions. This 

 was not due, however, to the diluteness of the solution, for in culture 

 solutions containing only 4 parts per million of potash as potassium 

 chlorid the plants were able to more than double their potash content in 

 10 days. The addition of nitrogen and phosphoric acid to the solutions 

 did not modify the nonavailability of the potassium in the orthoclase 

 solutions. 



In series c the cultures were maintained for 17 days, all solutions being 

 changed daily. Nitrogen and phosphoric acid were added to one culture, 

 the sodium base being omitted. The results again showed no marked 

 absorption of potassium from the orthoclase solutions. 



The plants in series d were grown for 15 days. The analyses, as in the 

 preceding experiments, showed no appreciable absorption of potassium 

 by plants grown in orthoclase solutions, but a marked absorption was 

 observed by plants grown in solutions of potassium chlorid. The presence 

 of gypsum or orthoclase in the potassium chlorid solutions did not mod- 

 ify the rate of absorption of potassium from these solutions by the 

 wheat seedlings. 



The results in Table I, taken as a whole, show that the potassium in 

 orthoclase solutions is not absorbed in measurable quantity by the wheat 

 seedlings. On the other-hand, potassium in potassium-chlorid solutions 

 of equivalent concentration is readily absorbed by the plants. 



