OBSERVATIONS ON THE ROOT NODULES OF SHEPHERDIA

Nodulated plants of Shepherdia canadensis have been raised in solution culture and shown to be able to grow and increase their nitrogen content in a solution free of combined nitrogen. A fixation of atmospheric nitrogen by the nodules is indicated by the data obtained, and under the prevailing conditions it attained a maximum of about 8 mg. per plant during the first season of growth from seed. The nodule development was secured by the application of an inoculum prepared from nodules of the related genus Hippophaë. Nodulation occurred at pH 6 and 7 but not at pH 5; it was also suppressed by the presence of small amounts of combined nitrogen in the culture solution. The capacity of the nodulated Shepherdia plant to fix nitrogen is probably of ecological importance.