June, 1922] 



MUENSCHER - 



■ABSORPTION OF SALTS 



325 



how much ash might have been found in the plants if the salts in the solu- 

 tion entered with the water in which they were in solution. These data 

 show that in every case the quantity of salts in a volume of solution equal 

 to the volume of water absorbed and transpired was at least as great as the 

 quantity of ash found. In every case but one, namely, in the humid cul- 

 tures of the summer series, the plants took up. more water than was neces- 

 sary to supply the salts found, provided they all entered with the solution. 



Table 8. Comparison of the Average Quantity of Water Transpired with the Average Ash 

 Content per Culture under Various Conditions 



Summer Series 



Dry 



Humid 



Liglit .. 



Shade 



Winter Series 



Light 



Shade 



Light 



Cone, of 

 Solution 



.14% 

 .14% 

 .14% 

 .14% 



.07% 

 .07% 

 .28% 



Cc. of Water 

 Transpired 



350. 

 170. 



833. 

 400. 



659.6 



382.7 

 431.6 



Total Weight of 

 Ash' Determined 



.147 



•135 

 .322 

 .121 



.182 

 .087 

 .163 



Ash Equivalent of 

 Solution 



.2800 

 .1360 

 .6640 

 .3200 



.2638 



•I53I 

 .6906 



An examination of. the data presented in the above tables shows that 

 the relation between transpiration and the absorption of salts as deter- 

 mined under the conditions of these experiments varies with the method by 

 which transpiration is changed. If there is a definite relation between the 

 quantity of water transpired and the quantity of salts absorbed, one would 

 expect that doubling the transpiration in plants would considerably increase 

 the absolute weight and percentage of ash in plants. This is not the case. 



An examination of the data of dry weights, ash weights, and ash con- 

 tent expressed as percentages of dry weights presented in tables 1,2, and 

 5 shows that in general an increase in dry weight is accompanied by a rela- 

 tively greater increase in the ash weight. These data are brought together 

 for comparison in table 9. In the dry-humid cultures the slightly lower 

 dry weight of the tops, roots, and total plants of the cultures grown in the 

 humid chamber is in every case accompanied by a slight decrease not only 

 in absolute quantity but also in the percentage of ash. This same 

 relation between increase in dry weight and ash is found between the light- 

 shade cultures of the winter series. In the light-shade cultures of the 

 summer series a pronounced increase in the dry weight of the tops is also 

 accompanied by an increase in total ash weight, but the percentage of ash 

 is decreased from 20.34 to 18.91 percent. The percentage of ash in the 

 roots is increased from 20.35 to 30.55 percent when the tota;! dry weight 

 and ash are increased. This increase in the percentage of ash in the roots 

 was more than enough to balance the decrease in the tops, so that the per- 



