The Root-nodules of Myrica Gale, 
BY 
W. B. BOTTOMLEY, M.A. 
Professor of Botany in King's College , London. 
With Plates XI and XII. 
HE discovery by Hellriegel and Wilfarth in 1886, that the root-nodules 
X of leguminous plants are able to assimilate atmospheric nitrogen by 
means of the Bacteria present in the cortical cells, directed attention to the 
possibility of certain non-leguminous root-nodules having a similar function. 
The earlier observers failing to demonstrate the presence of Bacteria in the 
nodules they investigated, but finding the nodules, especially the older ones, 
filled with hypha-like threads, considered them instances of £ Wurzelsym- 
biosen ’ caused by mycorrhizal filaments. 
In 1896 Hiltner demonstrated the presence of Bacteria in the root- 
nodules of Alder and Elaeagnus , and showed that young Alder plants with- 
out nodules would not thrive in a nitrogen-free soil. When, however, these 
starved plants were inoculated with organisms from Alder tubercles, nodules 
were produced and growth was normal. He also demonstrated that the 
poorer the soil in available nitrogen, the greater is the number of root- 
nodules developed on the Alder roots, provided the necessary organisms are 
in the soil. Hence under conditions of nitrogen deficiency the number of 
nodules on the roots becomes a measure of the nitrogen assimilating 
activities of the plant. 
In 1899 Nobbe and Hiltner reported that the root-nodules of Podocav - 
pus were active agents in the assimilation of nitrogen. A Podocarpus plant 
possessing root-nodules was grown for five years in nitrogen-free sand, 
thriving well during the whole period. 
In 1907 the author demonstrated the presence of nitrogen-fixing 
organisms in the root-nodules of Cycas. 
Hitherto, these four groups of non-leguminous plants — Alder, Elaeag- 
naceae, Podocarpus , and Cycadaceae — have been the only ones recognized as 
possessing root-nodules concerned with the assimilation of atmospheric 
nitrogen. 
[Annals of Botany, Vol. XXVI. No. Cl. January, 1912.] 
