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AMERICAN JOURNAL OF BOTANY 



[Vol. 9. 



piring plants under the various conditions under which the plants were 

 grown. When the ash content is expressed as percentage of green weight, 

 the variation is from 12 to 22 percent between the high- ajid low- transpiring 

 plants. 



Table 7. Comparison of the Average Percentage of Ash in Tops, Roots, and Total Plants 

 {Averages of cultures in tables 5 and 6) 



Percentage of Ash Based upon Dry Weights 



Those who maintain that the salts enter and move within the plant with 

 the water might say that, under conditions of low transpiration especially, 

 a dilute solution entering a plant is not sufficient to supply all the salts that 

 it needs, and that therefore it absorbs additional salts from the solution in 

 which it grows to supply its needs. On the other hand, the plant which 

 transpires freely would absorb large quantities of solution in which are 

 taken up all the salts needed by the plant. Under such conditions low- 

 and high-transpiring plants might have the same ash content. Needless to 

 say, such a teleological explanation is worthless. 



Table 8 was prepared to determine whether the salts available in the 

 solutions in which the plants were grown might limit the amounts entering 

 the plants under any of the conditions under which the plants were grown. 

 The first column gives the concentration of Knop's solution used. The 

 second column gives the total water absorbed per culture. The third col- 

 urfin gives the total salts absorbed as determined by the ash found. ^ The 

 fourth column gives the ash equivalent of the solution,* which indicates 



' The initial ash content of the barley grains was so small that it was not subtracted 

 from the total ash found in order to get the total ash absorbed. Four lots of 100 uniform 

 barley grains each were analyzed for total ash content. The following data are given in 

 average values per single grain: Dry weight, 0.0251 g. Ash weight, 0.00067 g. Percent- 

 age of ash, 2.68. 



* The term "ash equivalent of solution" is an arbitrary phrase here employed for 

 designating the number of grams of total salts (NO3 excepted) which are present in a 

 volume of solution which is equal to the volume of water tran spired per culture. 



