20 THEORIES ON THE ABSORPTION OF NITROGEN 



Malpighi's theory, saw no inconsistency between under- 

 ground habitat and gall formation. 



Franck, in 1879, believed that these tubercles were a 

 disease provoked by insects of the name of Anthomyia ; but 

 Cornu, in 1876, after mistaking galls caused by eel-worms 

 occurring among the nodules, had already realized that the 

 nodules had no relation to these parasites. 



Bivona thought they were fungi developed on the roots, 

 while de Candolle and Julasne stated that they were merely 

 morbid tumours, or fleshy knots. 



Clos believed their formation to be due to the medium 

 in which the plants were cultivated, the tubercles of Legu- 

 minos^e being merely lenticels. 



Gasparrini, at Naples, in 1851, considered the swellings 

 on the Leguminosie to be root tips and called them spongy 

 tubercles owing to their property of rapidly regaining tur- 

 gidity in water after having been previously dried. 



De Vries (1877), Tschirch (T887), Van Tieghem and 

 Douliot (1888) regarded the tubercles as a special form of 

 root. 



The majority of writers believed in the action of some 

 Cryptogam; notwithstanding the fact that, in 1866 and 1867, 

 Woronin attributed the nodules to the influence of bacteria 

 and called attention to the bacilli which he discovered in 

 the protoplasm and which strongly resembled micrococci. 



Professor Vuillemin, of the University of Nancy, in 1888, 

 after an exhaustive investigation of their anatomical charac- 

 ters, declared the root tubercles of the Leguminos^ to be 

 Mycorhizse, that is to say, roots united symbiotically with 

 a living fungus. 



Thomas Jamieson, whom we have already quoted, be- 

 lieved that the tubercles were the scars of wounds provoked 

 by the attacks of fungi. The plant reconstructed its tissues, 

 which would then engulf the fungus and neutralize its 

 effects. 



Hellriegel and Wilfarth brought their remarkable work 



