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me may be of interest, though, of course, the subject is too broad 

 to be treated only in the most general way. 



This branch is included in the peculiar characteristic of the 

 Leguminos^e, which renders them able to produce more nitrogen 

 than plants of other families. I may be excused here for 

 bringing together a few statements probably familiar to you, 

 but which will serve to make clear the relation of this ques- 

 tion to the general one, as to the source of nitrogen for the 

 plant 



In nearly all text books in physiological botany, it is claimed 

 that green plants get their nitrogen chiefly from the soil in the 

 form of nitrates. The principal authority on which this rests is 

 the experiments of Boussingault, made forty years ago. These 

 experiments have never been refuted, although many other sci- 

 entists have reached conclusions directly opposite to those of 

 Boussingoult. For example, Ville, in Paris, claims to have 

 proven that certain plants do take part of their nitrogen supply 

 from the free nitrogen of the air. Lawes and Gilbert, of Eng- 

 land, on the other hand, claim that the evidence given of this is 

 not sufficient, in short, they claim to have disproved the conclu- 

 sions reached by Ville. Many others have experimented in this 

 field, but among the conflicting opinions w^e may select one or 

 two that have been decided by general consent to rank as facts. 

 These are, ist, that the plants of the family Gramineae obtain 

 ^heir nitrogen mostly from the soil, and that the amount of ni- 

 trogen produced by these plants is in direct proportion to that of 

 the soil where they grow. Second, plants of the family Legum- 

 inosae, without regard to the amount of nitrogen in the soil in 

 which they grow, produce two or three times as much in their 

 fruit as do the family Graminea^. These facts are so far recog- 

 nized, that the Leguminosae are called nitrogen producers, the 

 Gramineaj, especially the certrals, nitrogen consumers. 



This brings us to the subject at once, with the question: If 

 there is no direct relation between the amount of nitrogen in the 

 soil and that found to be produced by the plant, where does the 

 plant get it? If from the air, is it in the form of free nitrogen 

 or as ammonia? 



Many of the family Leguminosae are supplied with peculiar 



