432 BOARD OF AGRICULTURE. 



For this reason, the first successful attempts to study the 

 relations of the vegetable kingdom to these three agencies 

 date only back to the close of the past century. They are 

 largely the results of the labors of Lavosier and Priestley. 

 Foremost among the scientists who, at the beginning of the 

 present century, devoted some attention to the chemical 

 physiology of plants and the application of chemistry to 

 agriculture, are De Saussure and Sir Humphry Davy. The 

 former was the first who called attention to the variations of 

 mineral constituents in plants, and pointed out some of their 

 relations to the soil and growth of plants, whilst the latter 

 recognized already the atmospheric source of nitrogen for 

 plant growth. The works of these illustrious investigators 

 remained comparatively unknown to agriculturists until 

 Liebig, in his celebrated work, " Die Grund-satze der Land- 

 wirthschaft," in 1840, called the general attention to tlieir 

 excellence and importance. Although more exact analyses 

 of the ashes of plants had been accumulating, and some 

 interesting features of the results had been pointed out, — 

 as for instance the limited number and constant occurrence 

 of the same mineral elements, as well as their varying 

 proportions in the case of different plants, — no material 

 change of opinion regarding their possible more intrinsic 

 relations to plant life took place during the time which 

 passed between the first publication of the investigations of 

 *De Saussure and Davy, and those of Liebig. The year 

 1840 is, on this account, usually cited as the beginning of a 

 new era in the history of agriculture and its associated 

 branches. It is justly claimed as one of the most valuable 

 services which Liebig has rendered to scientific and practical 

 agriculture, that he demonstrated by the aid of previous 

 investigations, as well as his own, the true connection which 

 exists between soil and plant, and the intrinsic value of the 

 mineral constituents in the growth of plants. 



Accepting, as we do, Liebig's teachings that a certain kind 

 and certain amount of mineral elements are indispensable for 

 the complete development of a plant through all its various 

 stages of life, and that, in case the ash constituents of the 

 lant are not supplied in due time, the plant may come top 

 blooming, yet cannot produce a perfect seed, it becomes 



