November 1, 1912] 



SCIENCE 



583 



and properties of soil organic matter, and 

 I am very glad to be able to announce to 

 you the existence in the soil of organic 

 compounds decidedly beneficial to plant 

 growth. Here is, for instance, a specimen 

 of creatinine, a nitrogenous compound, 

 which we have isolated from soils. This 

 compound has always been associated with 

 animal material, but in addition to finding 

 it in soils we have also found it to exist in 

 many plant materials, for instance, in 

 wheat seeds, wheat seedlings, wheat bran, 

 in rye, clover, alfalfa, cowpeas and pota- 

 toes, and if, as is suggested by several 

 investigators, creatinine in the animal 

 arises as the result of the breaking up of 

 albumen, then it seems reasonable to ex- 

 pect that creatinine would be found in 

 practically aU plants. From the stand- 

 point of root excretion I should also men- 

 tion the fact that of samples of the same 

 soil planted and unplanted, the planted 

 soils give larger amounts of creatinine, 

 thus showing that the increase of creatin- 

 ine in the soil is connected in some way 

 with plant growth. When the roots of 

 wheat were bathed in water the creatinine 

 could also be found in the culture water. 

 One of the sources of creatinine in soils 

 would, therefore, seem to be found in the 

 presence of this compound in plants, since 

 by the decay of plants and by direct 

 sloughing or even by excretion, the creatin- 

 ine is left in water and soil. Its occur- 

 rence in stable manure and also in green 

 manures is another source, and its forma- 

 tion by soil organisms may be another. 

 Whatever its source, it occurs in soils, and 

 appears to be a normal and frequently 

 occurring constituent and is present in 

 amounts comparable with the amounts of 

 soil nitrates found in ordinary agricultural 

 soils. Its effect on plants, as I have im- 

 plied earlier, is decidedly beneficial. When 

 a series of cultures containing only potash 



and phosphates in varying proportions is 

 set up together with another set containing 

 in addition some fifty parts per million of 

 the creatinine, the increased growth in the 

 latter set is rather striking, fully com- 

 parable with the increased growth pro- 

 duced by nitrates under the same circum- 

 stances. When nitrates are present at the 

 same time, the additional effect of the 

 creatinine is not so marked, but an an- 

 alysis of the culture solution reveals the 

 fact that far less nitrates are used by the 

 plants in the presence of the creatinine, 

 although a larger plant growth takes place. 

 In other words, the plants absorb the cre- 

 atinine, make use of it in building up tis- 

 sue, and in so doing a diminished draft is 

 made on the supply of nitrates. It ap- 

 pears, therefore, that this soil constituent 

 is fully as valuable as soil nitrate, can be 

 present in amounts comparable to the 

 amount of nitrate in soils and is able to 

 replace the latter in its effect on plant 

 growth. The significance of this to agri- 

 cultural investigations is apparent. 



Nor is creatinine the only constituent 

 that behaves in this manner. The same 

 beneficial characters are shown by other 

 soil constituents, by the hypoxanthine and 

 xanthine, by arginine and histidine and by 

 nucleic acid. All these show the same 

 beneficial character on plant growth and 

 the same effect on the decreased nitrate 

 consumption. Based on the results of 

 these rather extensive investigations, I am 

 ready to formulate the theory that these 

 degradation products of protein are ab- 

 sorbed directly by the plant from the soil 

 and that the plant uses these units for 

 building up the complex proteins as far 

 as it is possible to do so. Nitrate is usu- 

 ally considered as the best form of nitro- 

 gen for plant food. In order to use nitrate, 

 a highly oxidized form of nitrogen, to form 



