November 1, 1912] 



SCIENCE 



585 



trates over all other fertilizers in the ease 

 of the harmful soil constituent, dihydroxy- 

 stearic acid. Guanidine is harmful and 

 dihydroxystearic acid is harmful, although 

 this manifests itself in a different way. 

 Nitrate increases the harmfulness of guan- 

 idine, but decreases the haimifulness of 

 dihydroxystearic acid. Here is an effect 

 of a fertilizer which is entirely unexplain- 

 able from the viewpoint of mineral re- 

 quirement or plant-food addition. 



Nor is this behavior of nitrate in influ- 

 encing the effect of these organic sub- 

 stances on plant growth and development 

 the only illustration of the influence that 

 different fertilizer salts can exert on the 

 action of the organic compounds on plants. 

 Cumarin is another substance which we 

 have studied quite thoroughly in its effect 

 on wheat seedlings. Besides decreasing 

 growth, it also has a very peculiar and 

 characteristic action on plants which en- 

 ables the experimenter to pick out 

 cumarin-affected plants at a glance from 

 those affected by any other toxic body 

 studied by us. The leaves are shorter and 

 broader than is normal for wheat and only 

 the first leaves are usually unfolded, the 

 other leaves remaining wholly or partially 

 within the swollen sheath. Such leaves as 

 do break forth are usually distorted and 

 curled or twisted. Now when cumarin is 

 contained in the culture solutions of the 

 various fertilizer salts, it is quite apparent 

 that neither nitrate or potash nor combina- 

 tions of these affect these characteristic 

 symptoms of cumarin poisoning, but the 

 slightest addition of phosphate causes a 

 very decided change in the appearance of 

 the plants, which increases with increasing 

 phosphate until nearly normal develop- 

 ment is obtained, as shown by compari- 

 son with the corresponding cultures with- 

 out cumarin. 



I must also cite to you the influence of 



quinone when similarly studied. The ef- 

 fect of quinone is decidedly different from 

 the effect of cumarin, which produced 

 short, broad, irregularly developed leaves 

 and stunted tops; the effect of quinone is 

 to produce long thin leaves, and tall slen- 

 der plants. The interesting part in this 

 connection, however, lies in the fact that 

 the growth in the cultures high in potash 

 was nearer to the normal than the growth 

 in either the mainly phosphatic or mainly 

 nitrogenous cultures, and was in fact poor- 

 est in the latter. Vanillin similarly 

 stiidied behaved like the dihydroxystearic 

 acid in that nitrates were the most efficient 

 aid to counteract its harmful effect on 

 plants. 



These experimental facts present much 

 interesting material for discussion from 

 various points of view, but I wish here 

 only to call your attention to the relations 

 between organic compounds, their effect on 

 plants, and the action of fertilizers in this 

 connection, which action is apparently 

 apart and in addition to any food value of 

 the fertilizer salts for plants in the usually 

 accepted sense. It is clear that in the 

 illustrations which I have here given you, 

 the various fertilizer salts acted differently 

 in overcoming the respective harmful ef- 

 fects of these toxic organic compounds. 

 The mainly phosphatic fertilizers were the 

 most efficient in overcoming cumarin ef- 

 fects; the mainly potassic in overcoming 

 the quinone effects; the mainly nitrogen- 

 ous fertilizers in overcoming the vanillin 

 and dihydroxystearic acid effects; and in 

 the case of guanidine, the mainly nitro- 

 genous fertilizers even had the effect of 

 increasing the harmfulness of this com- 

 pound. It is clear that the organic com- 

 pounds in soils, whether already isolated 

 and studied or yet to be found, are potent 

 factors in soil fertility as they have a direct 

 effect on plant growth and plant metabol- 



