50 CLOVERS 



within them in countless myriads. They gain an 

 entrance into the plant through the root hairs. The 

 exact way in which benefit thus comes to the clover 

 plants is not fully understood, but it is now quite 

 generally conceded that the nitrogen taken in by 

 these minute forms of life is converted into soluble 

 compounds, which are stored in the tissues of the 

 roots, stems and leaves of the plants, thus furnish- 

 ing an explanation to the increased vigor. It can- 

 not be definitely ascertained at present, if, indeed, 

 ever, what proportion of the nitrogen in clover is taken 

 from the air and from the soil, respectively, since it 

 will vary with conditions, but when these are normal, 

 it is almost certain that by far the larger proportion 

 comes from the air. But it has been noticed that 

 when soil is freely supplied with nitrogen, as in 

 liberal applications of farmyard manure, the plants 

 do not form nodules so freely as when nitrogen is 

 less plentiful in the soil. The inference would, there- 

 fore, seem to be correct, that when plants are well 

 supplied with nitrogen in the soil they are less dili- 

 gent, so to speak, in gathering it from the air. In 

 other words, clover plants will take more nitrogen 

 from the air when the soil is more or less nitrogen 

 hungry than when nitrogen abounds in the soil. 

 And yet the plants should be able to get some nitro- 

 gen from the soil in addition to what the seed fur- 

 nishes to give them a vigorous start. 



This power to form tubercles, and thus to store up 

 nitrogen, is by no means confined to clovers. It is 

 possessed by all legumes, as peas, beans and vetches. 

 It is Qlaitned that some of these, as soy beans, qow, 



