MISCELLANEOUS NOTES AND OBSERVATIONS. 
553 
the rains were Irequent, they were only slightly rubbed. Upon 
a comparison of these trees with others which were unwashed, the 
conjecture of the two great philosophers aforementioned was 
confirmed, the former having increased almost double the growth 
of the latter. The experiment was made upon several Beech trees 
and will probably be succeeded by others, which may produce con- 
siderable advantage with respect to rural economy.” — (Jen. Ev. Post, 
W. G. Clarke. 
Root Tubercles. — The importance of nitrogen to plant-life has 
long been known, but, until recently, it had been thought that it 
could only be assimilated by plants from its compounds in the soil, 
and that the nitrogen of the atmosphere was comparatively useless 
to the plant. Mr. Sutton, when President of this Society, gave an 
account of the process of nitrification which is carried on in the soil, 
resulting in the production of nitrites and nitrates from ammonia- 
compounds, by the agency of bacteria, which are specially known 
as nitro bacteria. It is from the nitrates that the majority of plants 
get their supply of nitrogen. But it lias been noticed that certain 
plants (Papilionaren) can flourish in soils from which all traces of 
nitrogen compounds have been carefully removed. These plants 
have been found to possess gall-like out-growths or tubercles attached 
to the roots. Similar structures have been found in intimate 
association with the roots of many other species of plants. Those 
from the roots of the Kobinia or false Acacia were brought to our 
notice by Mr. Bid well. It is thought by many modern botanists 
that these tubercles are, indirectly, the means by which (certainly 
in the order to which the Kobinia belongs) nitrogen is conveyed to 
the tissues of the plant, and there assimilated. The process has 
not, I believe, been thoroughly worked out, but the tubercles are 
considered to be a fungoid growth, which benefits itself, and assists 
its host-plant, by attachment to the roots, being, in fact a case of 
symbiosis, such as exists, or is supposed to exist in the connection 
between fungus and alga, in the lichen. The fungoid tubercle is 
the agency by which the free nitrogen in the atmosphere is conveyed 
to the roots in a condition suitable for absorption into the tissues. 
As far as I can make out, the details of the process are, at present, 
unknown. It is certain that there exists in t lie soil a bacterial 
organism which is capable of forming nitrogenous compounds from 
