46 



Table l\.—The Effect of Carbon Black, Distillation,. 



Ignition, and Precipitation, on Plant Growth in a 



Toxic Soil Extract 



Nature of Solution 



Av. wt. root and top from 



Peas 



Sorghum 



Tops Roots! Tops 



Roots 



Tap water 



Soil extract 



Volatile part of soil extract 



Non-volatile part of soil extract 



Soil extract and carbon black 



Soil extract and CaCU 



Soil extract precipitated with Ca (0H)o 



Soil extract ash T. 



Second leachings 



.2949 

 .1594 

 .2327 

 .3047 

 .2250 

 .3458 

 .3796 

 .2893 

 .3340 



.09211 



.06401 



.11291 



.12441 



.09031 



.1065 



.1358 



.11641 



.12141 



.0450 

 .0402 

 .0382 

 .0505 

 .0471 

 .0443 

 .0538 

 .0335 

 .0415 



.0181 

 .0075 

 .0206 

 .0128 

 .0096 

 .0106 

 .0177 

 .0107 

 .0103 



Photographs of the peas and sorghuni arc shown in 

 Phite II, figs. 1 and 2. Tap water was used m the ex- 

 traction of the soil, and as a check in the cultures. The 

 concentrated extract contained manganese equivalent 

 to 255 p. p. m. MnS04, and the second leaching con- 

 tained the equivalent of 17 p. p. m. The cultures grew 

 from September 3 to September 19, 1917. 



In the untreated soil extract, neither the peas nor the 

 sorghum developed scarcely any roots, the growth of 

 lateral roots being almost completely inhibited. The 

 short, thickened roots were much darker than the nor- 

 mal. The volatile part of the soil extract proved to 

 be a splendid medium for the growth of sorghum, — 

 very much better than the non-volatile part. Exactly 

 opposite results were obtained with peas, the volatile 

 part producing less root and top than the non-volatile 

 part. The tops of the peas grown on the non-volatile 

 part, however, were almost white at the time the pho- 

 tograph w^as taken, and some of the leaves had dead 

 margins. The tops of the sorghum plants were simi- 

 larly affected under the same conditions. Highly 

 bleached plants were also produced by the extract ash. 

 Carbon black slightly imi)roved the extract as shown 

 by root and top development of both the plants grown, 

 though the tops were yellow in both cases. Calcium 

 chloride added in sufficient amount to make a N/20 so- 

 lution, increased root and top development for both 

 plants, though the peas were benefitted more than the 

 sorghum as can be readily seen from the plant weights 

 and the photographs. In presence of calcium chloride 

 both plants produced tops of a normal green color. 



