THE ACQUISITION OF ATMOSPHERIC XITROGEX. 115 



been undertaken by different investigators. In beginning our 

 investigations it was found that no satisfactory summary of the 

 work was available in any language. For this reason a some- 

 what extended study of the literature of the subject was neces- 

 sary and the general facts obtained are herewith presented 

 by Professor Munson. The bibliography, although incomplete, 

 is given as an aid to others working on this subject. Chas. D. 

 Woods.] 



XITROGEX ACCUMULATING PLAXTS. 



The most important discovery in vegetable physiology in its 

 relation to agricultural science, which has been made during 

 the present generation, is that of the relation between microor- 

 ganisms and the acquisition of atmospheric nitrogen by plants. 



A review of the question of assimilation of free nitrogen by 

 plants would necessarily be disconnected, since the subject has 

 been approached from so many different points of view. It is 

 not our purpose at this time, however, to make an exhaustive 

 study of the subject, but rather to bring it into view and call 

 attention to its economic importance. 



The results of several hundred experiments have shown con- 

 clusively that many if not all of the more common species of 

 legumes are capable of using atmospheric nitrogen. Peas, 

 beans, vetches, clover, alfalfa, lupine, soja bean, sainfoin, serra- 

 della and many other species have been used in the experiments. 



NATURE OF THE TUBERCLE ORGAXISMS. 



The tubercles were observed as early as i6i5,*but their origin 

 and significance have not been well understood. At first the 

 tubercles were supposed by some to be caused by a parasitic fun- 

 gus; others supposed them due to the attack of insects or 

 worms (Anguillulidae.) They were then regarded as rudimentary 

 roots or as buds which might develop in case the plant did not 

 fruit. 



In 1866 Woroninf made a careful study of the subject and 

 found in the tubercles numerous bodies resembling bacteria. 

 Because of the regularity of the organisms which were often 





*De Lechamp, Histoire generate des plantes, cited by Vuilleuiin, Ann. d. Sci. 

 Agronorn. frang. et etrang., 1888, p. 96. 

 fMem. Acad. imp. des Sci. de St. Petersburg, t. X, (1866) No. 6. 

 8 



