320 
Journal of Agricultural Research 
Vol. XIV, No. 8 
Table I .—Cultural and biochemical characteristics of legume bacteria after two weeks at 
28° C. 
Name of organism. 
Mannitol 
agar, 
surface 
growth. 
Standard nutrient 
broth. 
Litmus milk. 
Bromcresol- 
purple 
milk 
reaction. 
Surface 
growth. 
Clouding. 
Reaction. 
Reduction. 
Alfalfa z. 
Abundant. 
Scanty.... 
None. 
Turbid.... 
.. .do. 
Alkaline.. 
.. .do. 
Alkaline. 
Do. 
Do. 
Do. 
Do. 
Do. 
No change. 
Alkaline. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Alfalfa 2. 
.. .do. 
Alfalfa 3. 
Abundant. 
M e mbra- 
nous. 
None. 
.. .do. 
.. .do. 
Alfalfa 4. 
... do. 
...do. 
flight at bottom 
Alfalfa s. 
M e mbra- 
nous. 
None. 
.. .do. 
.. .do. 
Alfalfa 6. 
.. .do. 
.. .do. 
Alfalfa 7. 
.. .do. 
...do. 
.. .do. 
do 
Alfalfa 8. 
Moderate.. 
.. .do. 
.. .do. 
Sweet clover 9. 
Garden pea 10. 
Abundant. 
Moderate.. 
. ..do. 
...do. 
...do. 
.. .do. 
Alkaline.. 
.. .do. 
Slight at bottom. 
No reduction.. ,, 
Field pea 11. 
Vetch 12. 
None. 
Turbid.... 
Alkaline.. 
.. .do. 
Red clover 13. 
Abundant. 
M e mbra- 
nous. 
...do. 
No reduction; slimy 
at top. 
Red clover 14. 
Common bean 15... 
Soy bean 16. 
Scanty.,.. 
Soy bean 17. 
Abundant. 
Moderate,. 
M e mbra- 
nous. 
Turbid.... 
Alkaline.. 
No reduction; slimy 
at top. 
Velvet bean 18. 
Lupine 19. 
Scanty.... 
Abundant. 
None.. 
Alkaline.. 
...do. 
None.,. t . 
Lupine 20. 
... do. 
Turbid.,., 
Slight At bottom n _ 
Lupine 21. 
M e mbra- 
nous. 
.. .do. 
...do. 
.. .do. 
No reduction; slimy 
at top. 
do 
Lupine 22. 
...do. 
...do. 
Lupine 23. 
Scanty.... 
None. 
... do. 
...do. 
No reduction. 
PRODUCTION OF NODUEES 
The final test of identity of a pure culture of the legume bacteria 
consisted in the formation of nodules on the legume from which the 
culture was obtained. Tor this purpose the leguminous plant and the 
microorganism were grown in large Pyrex tubes containing agar, under 
conditions which excluded all other forms of life. When nodules de¬ 
veloped, a new isolation was made from the nodule and the organism 
secured in this way was compared with the original culture. In several 
cases these new cultures were again tested under sterile conditions for 
nodule formation. The lupines failed to grow well in the large test 
tubes, and for this legume a mixture of sterilized sand and soil was used. 
In every case the organism caused the formation of nodules, while the 
roots of the control plants were entirely free of nodules. 
STAINING CHARACTERISTICS 
The bacteria from the nodule or from agar slopes stain readily with 
carbol-fuchsin, gentian-violet, or methylene-blue. Perhaps the best 
preparations were obtained from the use of carbol-fuchsin, followed by a 
slight decolorization with dilute alcohol. The organism is Gram-negative 
when ethyl alcohol is used in the decolorizing process. 
The number of flagella seems to depend on the source of the culture or 
on its age. This point, however, deserves more careful study. The fol- 
