SYMBIOTIC NITROGEN FIXATION 169 



few minutes as before to get a good suspension of the bacteria. 

 Pour enough of this suspension over the bean seed in large tanks or 

 similar receptacles to wet the seed thoroughly, but not enough to 

 allow any excess of water. Then spread the bean seed out on a 

 canvas in a thin layer in the shade. As soon as the seed is air-dry 

 and will not stick, place in a planter and plant immediately. In 

 cases in which only small quantities of seed are to be planted, the 

 suspension need not be made, but the inoculated soil in small quan- 

 tities can be mixed with the seed in the planter and allowed to 

 drop with the beans as they are dropped from the machine, thus 

 introducing the bacteria into the soil with every seed, or nearly so. 



"Alternative Method. — Where it is not desired even to pur- 

 chase one commercial culture, inoculation can also be carried out 

 entirely successfully by obtaining soil from a garden in which 

 beans have grown successfully for some years and using that soil 

 for making up the soil suspension or for mixing with the seed as 

 above described. In other words, this garden soil, which contains 

 the necessary bacteria, will serve fully as well as the inoculated 

 and incubated soil just described above. This is of course the 

 simpler method to those who have access to garden soil which has 

 produced beans successfully. Soils like this may also be obtained 

 from old and more extensive bean fields, where successful bean- 

 growing has been carried out. For small plots, such soil can be 

 directly harrowed into the soil to be inoculated after being spread 

 (about one bushel per acre) in moist condition on a cloudy or 

 rainy day." 



Hope of the Future. — ^The discovery of the legume bacteria 

 and the learning of the conditions under which they fiX atmos- 

 pheric nitrogen has removed the nitrogen problem in so far as the 

 legumes are concerned, as they can now be grown on soil devoid 

 of nitrogen, provided they are properly infected and the soil is 

 otherwise suited to their growth. But how about the non-legumes? 

 Are there no organisms which will live in symbiosis with these 

 and thus render them independent of soil nitrogen? A number 

 of investigators have asked these questions and attempts have 

 been made to answer them. The legume organisms have been 



