898 The American Naturalist. — [ October, 
ROOT TUBERCLES OF LEGUMINOSAE. 
By Erwin F. SMITE. 
Among those who have contributed to our knowledge of 
this subject are Beyerinck, Frank, Ward, Hellriegel, Prazmow- 
ski, Nobbe, Schlossing, Laurent and Windogradski. The ques- 
tion of the symbiotic relationship of the bacilli, which are cer- 
tainly present in the tubercles, has received rather more 
attention from these investigators than have the bacteria 
themselves. The latter are the subject of an interesting paper, 
“Die Bakterien in den Wurzelknéllchen der Leguminoseen,” 
by Mr. Gonnermann in Landw. Jahrb., XXIII (1894), Heft., 4, 
5, pp. 649-671. The first part of the work was done at the 
Agr. Exp. Sta. in Rostock, and the rest in the Hygienic Lab- 
oratory at Danzig, and the internal evidence of the paper indi- 
cates a careful, competent man. The one question which the 
author at first set out to solve by means of purely bacteriologi- 
cal methods was, What bacterium causes the tubercles? Pure 
cultures were made from the bacteria occurring inside the 
tubercles and their behavior first studied on ordinary culture 
media—gelatine, agar, potato, bouillon, etc. Subsequently, 
lupine gelatine was used, and proved very suitable, the germs 
growing in it about equally well, whether slightly acid, slightly 
alkaline or neutral. The colonies which appeared on this 
gelatine were then inoculated into various media, from the 
plates to stick cultures, from these to potato, from the latter to 
agar, from agar into hanging drops, from these to plates once 
more, and so on, to insure purity and absolute certainty of the 
final results. To obtain material for making infections, unin- 
jured tubercles were washed in ordinary water and the earth 
rubbed away with a tooth-brush, then washed several times in 
distilled water, and finally put for several minutes into 1-500 
solution mercuric chloride. They were then thoroughly 
washed 3-4 times with sterile water, placed under a bell-jar on 
a glass plate previously heated to 150° C., cut open with a 
