1895.] Root Tubereles of Leguminosae. 903 
tural Experiment Station. Experiments by the author con- 
firm Hellriegel’s view that the tubercle bacilli are not capable 
of changing ammonium salts into nitrate, and the evidence is 
very good that these organisms are not the same as the nitrify- 
ing ferments of Windogradski. The Y-form occurs sparingly 
outside of the tubercles in various parts of the plant. The 
author also isolated B. tuberigenus from tubercles found on 
the roots of the rape plant. His general conclusions are as fol- 
lows: 
(1). The root tubercles of the Leguminosae are not caused 
_by a single specific bacterium but rather by several, one in one 
locality, another in another locality. 
(2). The Y-forms are zoogloea (Gebildkomplexe) which arise 
in the plant during the symbiotic or parasitic relations, and 
later when the tubercles rupture, they break up into the indi- 
vidual bacteria. These pass into the soil, form spores, and in 
the spring, as bacilli, once more enter the plant to again be- 
come Y-complexes during its growth. 
(3). The symbiotic relations are not yet known with certainty, 
tor of themselves the tubercle bacteria of the Leguminosae are 
not capable of rendering free nitrogen useful to the plant ; much 
rather is the plant in condition of its ownself to take up and use 
elementary nitrogen without fungous symbiosis. The bacteria 
aid the plant in doing this and may contribute in part toa 
higher nitrogen content. Finally, it appears to be established 
that in spite of the presence of the bacteria the plants do not 
take up any excess of nitrogen. From the many sided experi- 
ments which have been made, it follows also that not merely 
symbiotic but also parasitic influences are at work, and that the 
function of the bacteria as well as the method of assimilation 
of free nitrogen is not yet known with any certainty. 
