576- CONDITION OF THE SOIL. 



following 



5, 



Article No. 561 in our last issue, I 

 extract from Agricultural News of 



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|N confirmation oi 

 clip the 

 I December 



BACTERIOLOGY AND AGRICULTURE. 



The following report of a lecture recently delivered at Oxford by 

 Professor R. Warringnon on ' The Assimilation of Atmospheric 

 Nitrogen by the Agency of Soil Bacteria' is taken from the Agricul- 

 tural World of September ;"> : — 



" Nitrogen had long been known to exist in plants, but until 

 quite recently the original source of it was but very imperfectly 

 understood. It was known that a certain amount was supplied in the 

 shape of manure to the growing crops, but careful experiments 

 showed that, in some cases, more nitrogen was contained in the 

 mature plant than could have been obtained from the manure and 

 soil together. Particularly was this noticeable with leguminous 

 crops, such as clover, beans, peas, etc. Moreover, it was also found 

 that besides containing more nitrogen in themselves, leguminous 

 plants actually left more in the soil than was there at first, whilst 

 cereals reduced the quantity and exhausted the land, thus necessita- 

 ting the ' rotation of crops,' so well known in practice to every 

 farmer. Whence, then, came the extra amount of nitrogen ? An 

 obvious theory was that it might come from the atmosphere, but 

 investigations, made by Boussingault, Lawes, Gilbert, and Pugh, 

 appeared to show that the plants had no power of directly assimilating 

 free atmospheric nitrogen. A characteristic feature of all legumi- 

 nous plants was the nodules, or small rounded lumps, which were 

 attached to their roots ; and it was demonstrated by Hellriegel 

 and Wilfrath that when the plant was grown in sterilized sand, the 

 nodules did not appear and the plant did not develop. If, however, a 

 very minute quantity of ordinary fertile soil were added, the nodules 

 immediately formed, the plant grew vigorously, and subsequent 

 analyses showed that it contained far more nitrogen than was fur- 

 nished by the seed and the soil. Schloesing and Laurent, experi- 

 menting with plants growing in fertile soil, proved that leguminous 

 plants did actually consume atmospheric nitrogen ; and on studying 

 the nature of the nodules, Woronin. Marshall Ward, and others 

 found that they contained a certain bacillus which, when associated 

 with the plant, was capable of assimilating nitrogen from the air. 

 and ultimately supplying it to the plant in the form of proteids. 

 Attempts had thereupon been made to provide cultures of these 

 bacteria on a commercial scale under the name of ' Nitragin," but in 

 practice their use had been found to be wholly superfluous, and the 

 manufacture had been discontinued.*' 



LiBRAR 1 

 NEW YOI- 

 BOTANIC/ 



GAi- 



577. -MICROBES AS POLICEMEN. 



Sir William Crookes, giving evidence before the London Water 

 Arbitration Board yesterday, said that he and Professor Dewar. in 

 making daily analyses of the various supplies of London water, acted 

 as the candid friends of the water companies. 



