14 MAINE STATE COLLEGE 



3. All the plants were benefited by the addition of the 

 acid rock. The barley, and corn show the most marked increase, 

 the yield being - double that from the crude rock. The ruta-bagas and 

 the turnips derived nearly as much benefit from the crude rock as 

 from the acid rock. 



The effect of the acid rock was Terj r marked, with all the plants 

 grown, those receiving it, in nearly all cases, at once taking the lead 

 and keeping it to the end. The plants were darker green in color, and 

 the tubercules, which were developed on the roots of nearly all the 

 leguminous plants, were larger and much more numerous. It was 

 noticeable, however, that in some cases, especially with the clover, 

 turnips and ruta-bagas, the good effects of the acid rock were more 

 marked during the first few weeks of growth than at a later stage, 

 when the roots had become more fully developed and had begun to 

 forage for themselves. It would appear that the young plants feed 

 but little upon the insoluble phosphates; but that the organic acids 

 present in the sap of the roots exert a solvent action upon the in- 

 soluble phosphates in the soil, gradually converting them into avail- 

 able forms. 



