1906] BREAZEALE—EFFECT OF SOLIDS UPON GROWTH 57 
for ten years without fertilizer, and was acid to litmus paper. Te 
make absolutely sure that the effect of carbon black was not due to 
any substance added with it, the distilled water for the soil extract 
was shaken with the solid carbon black and filtered through a 
Fic. 2.—Experiment IV; 36 wheat plants grown 13 days. 1, extract of Miami 
silt loam; 2, the same with ferric hydrate; 3, the same with carbon black; 4, the 
Same with ferric hydrate, carbon black, and calcium carbonate. 
Pasteur-Chamberland tube before being used. Ferric hydrate, car- 
bon black, and a mixture of these two bodies, together with calcium 
carbonate, were used in this case. The plants are shown in jig. 2. 
From this experiment and others of similar nature it seems clear 
