172 AIR AND LIFE. 



agriculturists and horticulturists concerning sympathies and antipa- 

 thies between plants, and like matters. 



The quantity of nitrogen which leguminous plants can obtain from 

 the atmosphere by means of the bacteria which live on their roots may 

 be very considerable; it may amount to 100 or 150 kilograms per hec- 

 tare (2£ acres). Hence, it is an excellent plan with soils deficient in 

 nitrogen to grow and turn under leguminous plants. It follows also 

 that if a given soil seems unfit for the culture of a particular legumin- 

 ous plant, this may be because it does not contain the necessary bac- 

 teria, and under such circumstances all that is required is to inoculate 

 it. A culture is not required; it is enough to sprinkle some earth 

 taken from a field in which leguminous plants of the same species have 

 grown and thriven. The bacteria abound in that earth, and at once 

 multiply in the field. This is no matter of mere laboratory experiment; 

 the process has been tested on a large scale at Meppen in Germany, 

 by M. Salfeld, with the best results, the crop having been then doubled 

 and trebled. 



This inoculation may be performed in another manner. M. Breal, 

 of the Paris Museum of Natural History, grows two lupines in sepa- 

 rate pots, filled with sterilized earth. He inoculates the roots of the 

 one with a needle dipped previously in a culture of the appropriate 

 bacterium, while the other is not inoculated. The result is that the 

 former thrives, while the latter remains puny and perishes. 



Besides, Schloesing and Laurent have shown that if different legu- 

 minous plants are cultivated in a confined atmosphere the amount of 

 nitrogen in the air decreases. 



The general result of the very important labors of Hellriegel and 

 Wilfarth, of Nobbe, of Sir John Lawes and Sir Henry Gilbert is, then, 

 the discovery that different plants of the leguminous family — belonging 

 in particular to the papilionaceous division — are endowed with a very 

 special mode of nutrition, quit' 1 different from that of other phanero- 

 gams. By means of the cooperation of a few micro-organisms which 

 dwell in and on their roots, they are enabled to draw free nitrogen from 

 the air; not ammonia, nor any other form of combined nitrogen, but free 

 nitrogen, which is used as a nutriment. And thus it happens that that 

 enormous quantity of nitrogen which goes to make a large propor- 

 tion of the atmosphere, instead of being useless as it seemed at first, 

 is of very great importance to plant life. The probabilities are that it 

 is even greater than it now appears. We feel it difficult to conceive 

 that only a small proportion of plants are able to avail themselves of 

 this source of nitrogen, and physiology teaches us that so far as the 

 principal functions of life are concerned there reigns great similitude 

 in the processes by which they are effected. That papilionaceous 

 plants only, of the whole host of the vegetable world, should be able 

 to acquire nitrogen in the manner described seems unlikely, and thence 

 the opinion that a similar process and a similar function must obtain 



