33^ . POPULAR SCIENCE MONTHLY. 



substance of the Leguminosse. In some cases the bacteria can also be pre- 

 pared for transport in fluid cultures. The eolonies in the agar-gelatin are dis- 

 tributed in water, together with the agar-gelatin, by the user (after removing 

 the stopper) in the proportion, for example, of the contents of one glass tube 

 to from one to three liters of water, which is previously mixed with a suitable 

 material, such as an aqueous extract of the green substance of Leguminosse 

 sugar asparagin, for propagating the bacteria. This propagating material is 

 delivered with the bacteria tubes. Preferably the glass tube is laid in the 

 water until the agar-gelatine is dissolved. 



Immediately before sowing, the whole of the emulsion prepared as above 

 mentioned is poured over the seeds. The amount of water added for each kind 

 of seed is so proportioned that after the seeds have been thoroughly and uni- 

 formly moistened by a careful working over by hand, a surplus of liquid will 

 still remain. For clover-seed, for example, for twenty kilograms of seed the ad- 

 mixture of three liters of water with the contents of three glasses of inoculating 

 material (each glass containing, for instance, three cubic centimeters agar- 

 gelatin with pure cultures) is sufficient. For more bulky seeds a somewhat 

 larger amount of water is required. A sufficient quantity of dry sand or 

 earth from the field to be sown is then gradually added with careful stirring, 

 until the body of seed is in a suitable condition for sowing by hand or by means 

 of a sowing machine. 



This microbic (rhizobic) soil fertilizer for leguminous plants was 

 given the commercial name 'nitragin, ' and its efficiency was quite 

 carefully and extensively tested and commented upon by European and 

 American investigators. The consensus of opinion seemed to be that 

 it was of doubtful practical utility for agricultural purposes. Some 

 authorities maintained that it was of unquestionable value in virgin 

 soil. In rich and otherwise favorable soil conditions it is of only 

 sliglit value. It is maintained that nitragin aids very materially in 

 developing and ripening the fruit. As becomes evident from careful 

 consideration, the value of this microbic fertilizer depends upon whether 

 it will cause an increased development in the number and size of root 

 tubercles over and above those which would develop without the pres- 

 ence of this artificial aid. If the soil is already well supplied with 

 rhizobia or root tubercle bacteria, as soil naturally would be if the 

 leguminous plants under consideration had been grown in it for one 

 or more seasons, nitragin would in all probability be of little or no 

 value. In any case the anticipated practical results have not been 

 realized, as I am informed by a letter from Victor Koeclil & Co. of 

 New York City which states that 'nitragin is withdrawn from the 

 market and is no longer manufactured.' 



A second and later improvement in the method of inoculating seeds 

 with root tubercle bacteria (rhizobia) is given by Hartleb in the fol- 

 lowing specifications forming part of letters patent No. G74,7G5, 

 granted May 21, 1901, at Washington, D. C. : 



Be it known tliat I, Richard Hartleb, a citizen of Germany, residing at the 

 Botanisches Institute der Hochschule, Aachen, in the Empire of Germany, have 



