1906] BREAZEALE—EFFECT OF SOLIDS UPON GROWTH 59 
acid, fails to show any material difference between the good and the 
poor varieties of these soils, although they are agriculturally quite 
different. These cultures were grown under the direction of Mr. 
F. D. GARDNER, in charge of the Division of Soil Management, of 
this Bureau. They consisted of forty-eight plants and were grown for 
1, extract of Cecil 
.—Experiment V; 48 wheat plants grown 15 days. 
clay, ey 2, the same, filtered from carbon black; 3, extract of Cecil clay, poor; 
4, the same, filtered from carbon blac 
fifteen days. The results are given in Table II; percentage increases 
are given for each treated extract compared with the same extract 
untreated considered as unity. 
It will be seen from this table that the extract of good Cecil clay 
