696 SCIENCE PROGRESS 



Supposing the enzyme or something very near to it were to 

 preside at the birth of the compound, acting after the manner of 

 the last upon which the shoemaker makes the shoe, we have a 

 picture which probably is not far removed from that which 

 would be revealed to us could we see the process at work in 

 plant and animal — the directive agency — the outcome of which is 

 the formation of one particular type of asymmetric compound. 



Such in brief appears to be the philosophy both of progressive 

 and of retrogressive change in plant and animal. 



Questions of extraordinary interest and importance centre 

 around the problem of the origin of the nitrogenous constituents 

 of plants, especially of the albuminoids or proteins. First comes 

 the question of the supply of nitrogen to plants. As you know, 

 in practice this takes the form either of ammonia salts or of 

 nitrates or of vegetable or animal matter containing assimilated 

 nitrogen ; in whatever form it be supplied, however, there is 

 reason to suppose that it comes into action in the form of 

 nitrate. The ammonia of ammonia salts and the ammonia 

 derived from nitrogenous organic matters by their decay — 

 apparently under the influence of organisms in the soil — under- 

 goes oxidation within the soil at the instance of nitrifying 

 bacteria ; it does not seem to be available directly. Possibly — 

 nay, probably — the nitrate undergoes reduction within the 

 plant into hydroxylamine. But in the case of leguminous plants, 

 a marvellous symbiotic mechanism is come into existence, 

 whereby the plant is enabled to utilise nitrogen derived from 

 the atmosphere ; you probably know that nodular growths form 

 upon the roots and that in these bacteria abide which, we 

 believe, are the active assimilating agents. From a chemical 

 point of view, the whole process is most mysterious and 

 marvellous ; but there is no problem in agriculture which is so 

 important a one to solve in the interest of future generations. 

 Our stores of ammonia and of nitrates are rapidly being 

 depleted ; it is scarcely probable that the methods of making 

 these substances artificially will satisfy the demand that must 

 arise in the future. A great extension of the natural process of 

 accumulating nitrogen from the atmosphere is therefore to be 

 desired. 



As the albuminoids, like the carbohydrates, are all optically 

 active and apparently members of one class, it is not improbable 

 that their genesis is in some way bound up with that of the 



