lOO 



Journal of Agricultural Research voi. xviii, no. 2 



'plants as described above to distilled water and after several days have 

 analyzed the solution. The composition was found to be as follows: 



p. p. m. 



NO3 None. 



PO4 5-7 



K 1.2 



P. p. m. 



Ca 19. o 



SO4 None. 



Mg I. 7 



Ca and PO4 were thus the principal elements leached out. It will be 

 recalled that in sand cultures of series 2 and 3 considerable accumulation 

 of Ca and PO4 occurred in the roots. 



In order to compare absorption at different periods of the growth 

 cycle, analyses of solutions were made after the plants had absorbed for 

 a period of a week from solutions of 0.90 atmospheres concentration 

 with reactions of Pg 5.1 and 6.8. The periods chosen were 4 to 5 weeks, 

 6 to 7 weeks, and 11 to 12 weeks. In Table XII are shown the total 

 quantities per plant and percentages of the various elements absorbed. 



TABI.E XII. 



-Absorption of elements at different stages of growth O' 

 [Absorption period seven days) 



PARTS PER MILLION OF SOLUTION ABSORBED 



Period of growth. 



S04. 



4 to ■; weeks . . . 



Do 



6 to 7 weeks 6 . 



Do 



II to 12 weeks. 



Do 



NUMBER OF GRAMS ABSORBED PER PLANT 



4 to 5 weeks . . . 



Do 



6 to 7 weeks . . . 



Do 



II to 12 weeks. 



Do 



o. 021 

 .oil 



• 03s 



.032 

 .036 



.040 



PERCENTAGE OF TOTAL QUANTITY ABSORBED 



4 to 5 weeks . . . 



Do 



6 to 7 weeks . . . 



Do 



II to 12 weeks. 



Do 



6.0 



20. 6 

 16. 9 

 20. 9 

 20.5 



" Studies made on composite solutions, each representing 20 plants with 2 plants per liter of solution. 

 ^ Computed from 9-day absorption period. 



It will be noted that the total quantities and percentages were consider- 

 ably greater in the two later periods as compared with the first period. 

 Absorption in the eleventh to twelfth weeks was not greatly different from 

 that in the sixth to seventh weeks, except that in the latter period the 

 absorption of PO4 was decidedly increased. In each period the absolute 

 quantity of PO4 absorbed from the acid solution exceeded that from the 



