32 THEORIES ON THE ABSORPTION OF NITROGEN 



the infusion ceased growing and their organs faded. This 

 state of affairs only lasted a few days, the actual period 

 depending on the ultimate reserves in the seed. Then, all 

 at once, the influence of the infusion began to make itself 

 felt. The organs, stunted but not yet withered, took a fresh 

 lease of life, the chlorophyll was reformed, fresh leaves were 

 seen to sprout, and the plant, entering the assimilatory stage, 

 throve anew. 



Hellriegel and Wilfarth have endeavoured to prove that 

 it is during the period of inanition and before assimilation 

 and consequent growth that the nodules are formed. They 

 showed on trial plants that the roots never bore nodules 

 during germination, and at the beginning of the period of 

 inanition ; they only appeared in the final stage when the 

 leaves were becoming green. 



The nodules then cannot serve as storehouses, for it is 

 impossible to explain how a plant, with growth hindered by 

 lack of food, can, notwithstanding, find food for storage 

 purposes. At the same time, we have, in the action of the 

 soil infusion, an additional proof of the co-operation of an 

 external agent, and this latter can only be the micro- 

 organisms of the earth. 



Thomas Jamieson. 



Although the theory of Hellriegel and Wilfarth is to-day 

 almost universally accepted, a Scotch scientist, Thomas 

 Jamieson, Director of the Agricultural Station at Aberdeen, 

 after thirty years of stubborn experimental work, has come 

 to an entirely different conclusion as to the method by 

 which the Leguminosae fix atmospheric nitrogen. As we 

 do not wish to pass over any work dealing with this problem 

 we shall now give an account of Jamieson 's theories and 

 experiments. 



Firstly, the author aims at proving that the formation 

 of nodules on the roots of Leguminos^ is the effect of the 

 attacks of a fungus perfectly incapable of fixing atmospheric 



