Jan. 3,i92i Nodule Bacteria of Leguminous Plants 553 



tion. The flagella visible therein were all very weakly stained, so that 

 no definite conclusion could be drawn. A culture, for which we are also 

 indebted to Dr. Wilson, behaved in our hands like all those tested before; 

 practically all cells were distinctly monotrichous. A comparison of 

 Plate 68, A, with the pictures published on Plates IV and V of Bulletin 

 202, Illinois Agricultural Experiment Station (6), leaves no doubt about 

 this point. 



In Barthel's paper (2, p. 16) two drawings and one photomicrograph 

 are to be found which clearly illustrate the following statement : 



Bei den Lupinenbakterien sind die Geisseln ziemlich lang, wellig geformt und an 

 einem Pole befestigt. Ihre Anzahl variiert von 1 bis 6. Ihre Placierung ist recht 

 eigentiimlich. Sie sitzen namlich ofters nicht gerade an der Spitze des Zellleibes, 

 sondern sozusagen an den "Ecken" und oft etwas von dem Hinterende entfernt. 

 Oft findet man auch eine Geissel an der einen "Hinterecke" und mehrere andere 

 zusammen an der anderen. . . 



Bei den Luzernebakterien waren die Geisseln meist weniger und kiirzer, am hauf- 

 igsten 1 oder, seltener 3 oder 4, aber auch hier deutlich lophotrich. . . 



Fred and Davenport (7), on the other hand, saw only one or two cilia 

 with the lupine bacteria, while several strains of alfalfa organisms left no 

 doubt as to their peritrichic flagellation. 



We believe that these conflicting views are in fact not so irreconcilable 

 as they seem to be. If well-made slides are examined carefully, some 

 cells will always be discovered which clearly show that on account of the 

 primary swelling and the following shrinking of their capsules, the flagella 

 are often more or less dislocated. Some of the cells shown in Plate 68, 

 A-C, exhibit this phase as clearly as it is possible in such reproductions. 

 The flagella of the monotrichous bacteria of the cowpea-soybean group are 

 to be seen in an exactly polar position only when the cells themselves are 

 lying lengthwise within the "drift," as indicated by the floating flagella. 

 In all other cases dislocations may take place, removing the cilia to the 

 corners or even to the side of the cells, where they should not be viewed, 

 however, as remnants of a peritrichic flagellation. 



On the other hand, analogous disturbances may cause the occurrence 

 of apparently cephalotrichic bacteria among the peritrichic cells of Ba- 

 cillus radicicola and B. radiobacter. That there exists no truly polar 

 flagellation in these cases, however, is evidenced by the fact that the cilia 

 composing such an apparently polar tuft do not protrude exactly from the 

 same spot, as they do, for example, in the cell with several polar flagella 

 shown in Plate 68, A. They are always more or less separated and are 

 only accidentally drawn together in the course of the shrinking of the 

 capsule. A thorough examination of well-made preparations leaves no 

 doubt that the original position of the flagella is peritrichic. 



SUMMARY 



(1) The nodule bacteria of the leguminous plants are to be divided into 

 two groups, differing morphologically as well as physiologically. 



