48 



Table Y.—The Effect of Distilled Water vs. Tap Water, 

 on the Toxicity of a Soil Extract Containing 60 



p. p. m. Mn. 



Culture Medium 



Peas 

 Wt. of air dry 



Roots Tops 



Sorghum 

 Wt. of air dry 



Roots Tops 



Tap water 



Distilled water 



Soil extract, untreated 



Volatile part of soil extract 



Non-volatile part of extract made to 



volume witti distilled water 



Non-volatile part of extract made to 



volume with tap water 



Extract evaporated, ignited, dissolved, 



made to volume with dist. water . 

 Extract evaporated, ignited, dissolved, 



made to volume with tap water 



Extract plus 2 gm. CaCO., per liter 



.1209 

 ,1318 

 .0550 

 .1267 



.0758 



.1626 



,0525 



,1686 

 ,1556 



.3005 

 .2118 

 .3819 

 ,1986 



.3497 



.3402 



,3125 



,3566 

 ,2971 



.0251 

 .0105 

 .0050 

 .0230 



.0344 

 .0269 

 .0286 

 .0304 



0051 .0208 



.0210 



.0063 



.0238 

 .0306 



.0310 



.0255 



.0340 

 .0399 



The data given in Table V fnlly confirm the sugges- 

 tion that the salts in the tap water used* in the previons 

 experiments were responsible for the reduced toxici- 

 t}' of the soil extract which had been concentrated and 

 again made to volume with tap water. The photo- 

 graphs shown on Plate III, figs. 1 and 2, shov/ conclu- 

 sively that concentrating the soil extract and making 

 it back to volume with distilled water, had no effect on 

 the toxicity of the solution; but when tap water was 

 used, both roots and tops grew very well indeed. Simi- 

 lar results were obtained by evaporating the extract to 

 drj^ness, igniting, and dissolving the residue in acid, as 

 previously explained. When made to volume with 

 distilled water, the toxicity was not reduced; but when 

 made to volume with tap water, both roots and tops 

 grew well. It should be stated, however, that in each 

 of the tap water dilutions, the plants produced yellow 

 tops. The untreated extract and the cultures made 

 to volume with distilled water produced tops with a 

 normal green color, but root growth was almost com- 

 pletely inhibited. Neither the sorghum nor the peas 

 made lateral roots more than a few millimeters long. 

 In the photograph, none of the sorghum roots in these 

 cultures can be seen, but the stubby pea roots may be 

 seen in tumblers No. 3 and 5. The soil extract to 



*Five hundred cc of the tap water used in this experiment 

 required 3.3 cc. of N/5 HCl to titrate, using methyl orange 

 as the indicator. 



