42 
SIR J. B. LAWES AilD PROFESSOR J. H. GILBERT OX THE 
fungus-mantle dies off on the older portions of the root, and its extension is confined to 
the younger roots—those which are active in the acquirement of nutriment. 
This fungus development was always observed in the case of teaks, beeches, horn¬ 
beams, and hazels:—in seedlings of 1, 2, or 3 years old, and in trees more than a 
century old. It was, however, not found on the roots of the associated woodland 
plants, even when these were growing close to a tuft of the mycorhiza. Nor was it 
found on the roots of maples, elms, alders, birches, mulberry, buckthorn, planes, 
walnut, apple, service-tree, hawthorn, cherry, cornel ash, syringa, or elder, &c. Thus, 
the majority of woodland trees appear to be free, and the occurrence seemed to be 
almost limited to the Cupuliferse; though outside of this family the development has 
nevertheless been observed, as on vfiUows, and some conifers; and it is supposed 
probable that it may be found to be more general as investigation extends. 
In the case of the Cupuliferm the occurrence seems to be universal. It has been 
observed in the mmst widely distant localities, at very different altitudes, in very 
different aspects, in soils of the most varied geological character, and with very varied 
amounts of humus, with great variation in the associated herbage, and even in a 
flower-pot. The growth is perhaps the most luxuriant on chalk soils. It is also the 
more developed in the first 2 inches, or the richer-in-humus layer of the soil. 
The occurrence of a fungus on the roots of certain trees has indeed been recorded 
before. It has sometimes been considered to be connected with a diseased condition, 
though it has also been noticed on healthy trees. The observations have, however, 
not before been generalised. 
Fuank considers that the conditions are those of true symbiosis. He m fact 
concluded that the chlorophyllous tree acquires the carbon, and the fungus the water 
and the mineral matters, that is the soil nutriment. 
Frank did not refer to nitrogen. But there is no reason to suppose that the 
fungus could not, as do the fungi in the case of fairy rings for example, avail itself of 
the organic nitrogen of the soil. 
Here then we have a mode of accumulation of soil nutriment by some green-leaved 
plants, which so far allies them very closely to fungi themselves. Indeed, it is by 
an action on the soil which characterises non-chlorophyllous plants, and by virtue of 
which they are enabled to take up nutriment not available to most green-leaved 
plants, that the chlorophyllous plant itself acquires its soil-supphes of nutriment. 
Under such circumstances, it can indeed readily be supposed that the tree may 
acquire not only water and mineral matter, but organic nitrogen from the soil, and if 
so probably organic carbon also. In reference to this point, it has already been 
stated that, from the evidence so far at command, it was concluded that the action is 
the most marked in the surface layers of the soil rich in humus. 
So far as this is the case, it is obvious that such an action of fungi on the soil does 
not aid us in the explanation of the acquirement of nitrogen from raw clay subsoil by 
the deep and strong rooted Leguminosm. Further, it is distinctly stated that the 
