ORIGIN AND FORMATION OF ORGANIC MATTER IN PLANTS. 913 



nitrate added. Iti Hellriegel's experiments less than 1 gm. of dry 

 matter was produced when nitrates were not added, the production of 

 dry matter increasing to 25 gm. when sufficient nitrates were supplied. 



These experiments, however, simply demonstrated in an exact man- 

 ner facts which were already well known in practice. The consumption 

 of nitrate of soda would never have reached its present enormous 

 proportions if farmers had not learned to appreciate the efficacy of 

 nitrates as a fertilizer. At the present time they enter into all fer- 

 tilizer formulas. The application of this fertilizer is necessary, because 

 we are not yet able to so control nitrification in the soil that it can be 

 made to furnish sufficient nitrates for the demands of the crop at 

 exactly the time in the spring when they are most needed. Nitrates 

 are produced only in warm and moist soils, and they are found in the 

 drainage water in larger proportion in autumn than in any other 

 season. Fortunately the roots of living plants have great capacity for 

 retaining the nitrates and thus reduce the loss in drainage. 



If wheat roots are drawn from the soil during the winter, dried, and 

 soaked in sulphate of diphenylamiu they will take on a deep blue 

 coloration. The amount of nitrates contained in wheat roots is sur- 

 prisingly large. The author has found as much as 1 per cent in dried 

 roots, but the proportion decreases as growth advances. They pass 

 from the roots to the stems and then to the leaves, where they are used 

 in the formation of albuminoid substances. It might be a matter of 

 surprise that substances which are so easily soluble in water as the 

 nitrates can nevertheless be taken up and retained by roots even when 

 surrounded by moist soil. Demoussy has shown that nitrates can not 

 be removed from the roots by washing in cold water, but are extracted 

 when the roots are treated with warm water or when they are subjected 

 for some time to an atmosphere of chloroform and then washed with 

 cold water. It appears, therefore, that the nitrates penetrate by 

 osmosis into the interior of the cells and form unstable combinations 

 with the protoplasm, resuming their normal state only when the 

 protoplasm is modified by elevation of temperature or the action of 

 chloroform. 



Experience has shown that whether nitrates are formed in the soil 

 by the action of micro-organisms or introduced in the form of fertilizers 

 they exert a decided influence upon the crop. Nitrates are not formed 

 in soils like those of meadows or forests, which are highly charged 

 with decaying organic matter, since these soils are acid and therefore 

 do not furnish a suitable medium for the nitric ferment. Liming ren- 

 ders such soils more favorable to the activity of the nitric organisms. 



In meadow and forest soils nitrogen appears to be taken up by plants 

 in the form of ammonia. Miintz, 1 Breal, 2 and Pagnoul 3 have reported 



'Ann. Sci. Agron., 1896, 1, No. 2, p. 161. 



8 Ann. Agron., 22 (1896), p. 485 (E. S. R., 8, p. 386). 



3 Ann. Agron., 19 (1893), p. 274. 



