NUTRITION 75 



the following season and then accomplish the infection of 

 the roots of the new crop. Infection takes place through 

 root-hairs attacked and entered by these bacteria.* The 

 bacteria may be grown in artificial culture media inoculated 

 from tubercles. In such cultures there is an appreciable 

 increase in nitrogen.! 



Leguminous plants will grow in sterilized soil containing 

 nitrates in forms and in quantities suitable for the successful 

 cultivation of other plants, but under the conditions em- 

 ployed in experimenting they do not produce crops so good 

 as when grown in unsterilized soil. The following figures 

 will indicate the benefit they derive from association with 

 the proper bacteria : X 



Per culture-jar, each holding two plants of Lupinus 

 luteu.s — 



I. WrrH TUBERCLE FORMATION 



grams ) . 



( ii and b ) watered with unsterilized lupin-soil water ( 40 

 grams ) . 



(c) was watered with sterilized (tap ?) water. 



It must be borne in mind, however, that though the legu- 

 minous plants may appear to profit by such association 

 with bacteria, these results are derived from experiments 



* Pelrce, G. J. Root^tubercles of Bur Clover and of some other legumi- 

 nous plants. Proc. Cal. Acad. Sciences, Botany, vol. II., 1902. 



t Maz^. Fixation de I'azotte libre par le bacille des nodosit^s des Legu- 

 mineuses. Annales de I'lnstitut Pasteur, t. XI., 1897. 



t Hellriegel und Wilfarth. Erfolgt die Assimilation des freien Stickstoffs 

 durch die Leguminosen unter Mitwirkung niederer Organismen? Ber. d. 

 Deutsch. Bot. Gesellschaft, Bd. VIZ., 1889. 



