It is, in fact, fully established that these leguminous crops acquire a considerable amount of nitrogen by the fixation of the free nitrogen of the atmosphere under the influence of the symbiotic growth of their root-nodule-microbes and the higher plant.
Eitel, knot, nodule, cf.
The heaviest nodule weighed over 20 tons.
In 1897 Peary brought the largest nodule to New York; it was estimated to weigh nearly loo tons.
The bacteria, which are present in almost all soils, enter the root-hairs of their host plants and ultimately stimulate the production of an excrescent nodule, in which they live.