BOT.-Vox.. II.1 PEIHCB-ROOT-TUBERCLES. 307 



adds to strengthen his comparison, " die WurzelknoUchen 

 sind kein Organwelches der Leguminose ursprunghch eigen 

 Tare ebenso'wenigwie dies bei den anderen Pflanzen der 

 Fall St. sondern eine erst von dem Rhizobrnm angeregte 

 Inn aber selbst aufgebaute Bildung." ,J"f ;7"' ^^^^^ 

 that he has repeatedly seen lupines, cutovated m terd.zed 

 and uninfected soil, which formed swellmgs on the oots 

 closely resembling young tubercles, but showing neither 

 tZlo. threads nor any traces of the cell-contents cha- 

 acteristic of true root-tubercles. He accounts for this not 

 on the ground of slight infections producing only abortive 

 tuberclfs, but on the hypothesis that the lupines, accus^ 

 tomed for thousands of years to symbiotic --tence wi* 

 the tubercle bacteria, have so firmly acquired the habit of 

 ming tubercles that they begin to form them even before 

 and without infection. On these points I wish again to call 

 attention to the fact that the tissues of the tubercle orig- 

 inate from the same layer of cells as g-« "f '^^^ Bunilar 

 divisions, to the lateral roots (see figs. 4. 5. f)- When one 

 compare; a very young mass of tubercular tissue still 

 enclosed in the cortex of the root, with a vjy y°ung 

 lateral root also still enclosed in the cortex of the root, the 

 resemblance between the two structures is strong. F gures 

 5 and 6 show this. Figure 5 is a diagram of a section in 

 Ihich a tubercle and a lateral root are growing -de by s.de 

 and from the same layer. In the figure the tubercle is to 

 the left, the lateral root to the right. Figure 6 is a drawing 

 of tube cle and lateral root on a larger scale, the root to 

 the right, the tubercle to the left. In the tubercle some 

 Infectfon threads show. The tubercle has the same form a 

 the root, but shows no differentiation among its cells, i he 

 lateral r;ot already shows a differentiation of dermatogen and 

 there is a foreshadowing of the vegetative point. Central 

 cylinder and periblem are not yet d'Stinguishable. The 

 cells of the tubercle are larger than those of the la eral 

 root, but the nuclei of the tubercle cells are not P-'OP- >»"- 

 a^ly larger and most of them are actually no larger than 

 those of the lateral root. 



