436 RELATION OF PLANT PHYSIOLOGY TO OTHER SCIENCES. 



sidedness of the perceptions of chemical analysis, which drew conclu- 

 sions as to the soil nourishment for vegetation only by comparing 

 soil analysis with plant analysis, could only yield a one-sided solution 

 of the question at issue, particularly that of plant nutrition. Not 

 until synthetical research as to the nutrition of plants made upon liv- 

 ing specimens could it be determined on the side of the plant what 

 elements taken up from the soil serve for food, what of the material 

 taken up is used for other purposes, and what is merely neutral. Thus 

 agricultural chemistry, under the influence of plant physiology, has 

 become transformed into agricultural physiology, which to-day is to be 

 counted one of the most important studies that contribute to practical 

 life. 



The fruitful cooperation of scientific learning and of agriculture and 

 industry may be illustrated by the following instructive example: 

 Long before Liebig's time the farmer knew that the cultivation of 

 leguminous crops would make the soil richer in nitrogen, in that nitro- 

 gen compounds accumulate that which can be assimilated by plants. 

 It was also known that leguminous plants produce peculiar little 

 tubercles on their roots, which were explained in most varied and cir- 

 cumstantial ways. Bacteriological investigation has shown that these 

 tubercles constitute the habitat of certain bacteria, which obtain 

 entrance into the roots of leguminous plants, and live there in the 

 mutually helpful relation of symbiosis. These bacteria, which live in 

 peas, lentils, lupines, etc., possess the remarkable capacity of bringing 

 the nitrogen of the air contained in soil into compounds which can be 

 assimilated by plants. Thus the old riddle was solved. If beans be 

 planted in sterilized soil they grow less vigorously than in ordinary 

 soil, which harbors the bacteria in question. Abundance of these 

 peculiar bacteria in the soil increases the productiveness of leguminous 

 crops. This knowledge has resulted in a new industry. In the famous 

 dyeworks of Meister & Lucius, in Hochst, is generated a product called 

 "nitragin" for the cultivation of lupines, peas, and other legumes. 

 This "nitragin" is simply artificially increased bacteria of different 

 species kept in the resting stage, which, added to the soil in which 

 lupines, etc., are planted, increases the available nitrogen supply. 



Similarly numerous other sciences were richly repaid in practical 

 help by plant physiology for what they had first furnished for " work- 

 ing capital" in the form of knowledge and stimulus. Therein, how- 

 ever, the account between theory and practice is not settled. That 

 great account will, indeed, never be canceled. With the advancement 

 of agriculture, of commerce and industry, arise continually scientific 

 problems, and new scientific learning and discoveries ceaselessly pro- 

 mote practice. Ever more and more is disappearing the old opposition 

 between science and practice, and more and more the opinion matures 

 that human progress rests upon the harmonious cooperation of both. 



The invasion into the realm of practical life by plant physiology has 



