CLOVER CULTURE. 137 



week the picture very suddenly and decidedly changed with- 

 out any apparent cause. No. 77 continued to be in a 

 starving condition, but two plants in 79 took courage and a 

 little later, two in 78 followed the example. Their sickly 

 green color gave place to a healthier, new leaves grew 

 stronger and broader and without consuming any of the 

 earlier developed leaves. From this time on they made 

 rapid growth and by the eleventh week they had overtaken 

 those abundantly supplied with nitrogen and passed many of 

 them. From this time on there was no relation or correspon- 

 dence whatever between development and the quantity of 

 nitrogen supplied, while the harvest bore the same general 

 result, and subsequent analyses showing, in some cases, 

 plants containing less nitrogen than had been given the 

 vessel in which they grew, in others more, and in some large 

 quantities of nitrogen where none at all had been given. 

 On this Prof. Helriegel says : 



Three years of this kind of experiment demonstrated two facts 

 clearly, first, that the legumes had found a source of nitrogen somewhere 

 else than in the soil, and that, second, they might or might not thrive 

 even though the soil was amply supplied with nitrogen in a form render- 

 ing it available for other plants in short, while the harvested plant con- 

 tained abundant nitrogen, whether the soil had or had not contained any, 

 Deemed to have no connection with or influence upon the amount con- 

 .tained in the plant. Chance seemed to rule. The thriving pea vine two 

 months old might fail utterly, although supplied with abundant nutri- 

 ment in the shape of complete fertilizers, or it might do well with one 

 from which nitrogen had been wholly omitted The first inference was 

 that the pea had some source from which to provide nitrogen other than 

 the soil, or, rather, some peas had and others, apparently under precisely 

 the same conditions, had not. What was the source? And why could 

 some plants draw on that source and others not? 



It is impossible for us to give details of all the experi- 

 ments undertaken to answer these two questions, for they 

 cover upwards of 200 pages of Prof. Helriegel's work, of 

 which we aim to give our readers only the substance. One 

 cannot read them without admiring the patience and intelli- 

 gent discriminations of the investigator, without admiring" 

 also the methods of true science which seeks to narrow 

 downward gradually by experimental proof until one by one 

 the facts are set aside as demonstrated, all bearing one way 

 and leading up to one inevitable conclusion. As stated 

 above, it was first discovered that plants that did well without 

 nitrogenous fertilizers had tubercles on their roots ; those 

 that did not do so well, had fewer, those that did not do well 

 at all, had none, or nearly none. The connection between 

 the presence of tubercles on the roots of the legumes and the 

 capacity to obtain nitrogen, where there was none in the soil, 



