782 The American Naturalist. [September, 
THE MORPHOLOGY OF ROOT TUBERCLES OF 
LEGUMINOS 2. 
ALBERT SCHNEIDER, M. D. 
The object of this research was to give a more detailed 
account of the anatomical structure of root tubercles, thus 
adding perhaps somewhat toward clearing up some of the 
difficulties in the comparatively little known field of teratology. 
It is true much labor has been expended in the endeavor to 
get a correct understanding of “symbiosis” and the relation 
of Rhizobia to certain plants. The life history and morphol- 
ogy of the root bacteria have received most of the attention 
while the tubercles themselves have been almost entirely for- 
gotten. Frank, who has done much in this line of research 
offers but little concerning tubercle morphology. Nearly all 
of his attention is directed toward the “Bakteroiden.” The 
same is true of Beyerinck, Brunchorst, Waronin and the others. 
Some of the pupils of Frank have also made noteworthy 
researches concerning Rhizobia. Recently Frank and Moeller’ 
have engaged in a controversy with regard to the “Dimorphis- 
mus der Wurzelknóllchen der Erbse.” Frank has also described 
the lenticular structure of root tubercles. Beyond this, little of 
importance seems to have been done with root tubercle mor- 
phology. 
In my own jac mature tubercles were taken from 
various Leguminose toward the close of the vegetative period, 
since at that time tissues have acquired their most marked 
morphological characteristics. The earlier stages of develop- 
ment were studied at various periods of the season. The final 
summing up was not completed until late in the year. (Dec., 
1892.) 
The tubercles are in themselves abnormal growths produced 
by the local irritation of certain organisms, the Rhizobia; and 
1 The investigations described in this paper were carried on in the laboratories of 
botany, of the University of Minnesota. 
* Berichte der deutsch. bot. Ges., Hefte 3 und 5, 1892. 
