THE CLOVER ROOT TUBERCLE. 



CHAPTER XIII. 



In previous chapters we have assumed certain facts,, 

 namely, that the clovers of all kinds fertilize the soil while at 

 the same time furnishing-, in the crop, a very large amount ol 

 nutritive material of the richest quality; second, that the fer- 

 tilizing- material furnished by the clovers is in the form ol 

 nitrogenous compounds which we have grouped under the 

 general name, nitrogen, and third, that this surplus of nitro>- 

 gen is obtained from the atmosphere through the medium of 

 the tubercles or nodules on the roots of the clovers, eighty 

 per cent, of the atmosphere being nitrogen, and therefore fur- 

 nishing an inexhaustible supply. 



Having assumed these facts so frequently and stated them 

 so confidently, it is but due to the reader that we should give, 

 in as brief and concise a manner as possible, the reasons for 

 this frequent assumption and confident statement. The fact 

 that clover adds materially to the fertility of the land on 

 which it is grown, notwithstanding the heavy drains it makes 

 upon its resources, is too well known to need argument. The 

 fact that this fertility is mainly in the form of nitrogenous 

 compounds might well be suspected from the fact that all 

 kinds of grain which make heavy drafts on the nitrogen in 

 the soil do better after clover than following any other crop,, 

 and has been very clearly proved by analyses of soils in pots on 

 which clover has been grown, the analyses having been made 

 both before and after growing the clover, and in a way whicfo 

 precludes any material errors. 



The fact having been ascertained that clover does in some- 

 way obtain a supply of nitrogen, under certain circumstances^ 



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