804 now CEOPS FEED. 



ishing solution, by the amount of free acid or of iron 

 present, nor by the illumination. Hamj)e observed that 

 from these trials it seemed that the j^lants^ while young^ 

 were unable to asshnilate ammonia or did so with diffi- 

 culty^ but acquired the 2>ovjer with a certain age. 



In 1868, Wagner {Vs. >S?., XL, 288) obtained exactly' 

 the same results as Ilampe. He found also that a maize- 

 seedling, allowed to vegetate for two weeks in an artificial 

 soil, and then placed in the nutritive solution, with phos- 

 phate of ammonia as a source of nitrogen, grew nor- 

 mally, without any symptoms of disease, Wagner ob- 

 tained one plant weighing, dry, 26' |^ grams, and carrying 

 48 ripe seeds. In experiments with carbonate of ammonia, 

 Wagner obtained the same negative result as Beyer had 

 experienced in 1866. 



Beyer reports {Vs. St., XI., 267) that his attempts to 

 nourish the oat-plant in solutions containing ammonia- 

 salts as the single source of nitrogen invariably failed, 

 although repeated through three summers, and varied in 

 several ways. Even with solutions identical to those in 

 which maize grew successfully for Ilampe, the oat seed- 

 lings refused to increase notably in weight, every precau- 

 tion that could be thought of being taken to provide 

 favorable conditions. It is not imiDossible that all these 

 failures to supply plants with nitrogen by the use of am- 

 monia-salts depend not upon the incapacity of vegetation 

 to assimilate ammonia, but upon other conditions, unfa- 

 vorable to growth, which are inseparable from the meth- 

 ods of experiment. A plant gro\ving in a solution or in 

 pure quartz sand is in abnormal circumstances, in so for 

 that neither of these media can exert absorbent power 

 sufficient to remove from solution and make innocuous any 

 substance which may be set free by the selective agency 

 of the plant. 



Further investigations must be awaited befoi-e this 

 point can be definitely settled. It is, however, a matter 



