THE FUNGUS-ROOT (MYCORRHIZA). 179
tissue. This attachment of fungus to root does not kill the
tree, we are not sure that it does any harm, it may indeed be of
considerable use to it. The immediate effect upon the root is
an arrest of the growth in length with more frequent branching,
that is, the formation of a fungus-root. The actual inception and
development of a fungus-root is not easy to follow. This close
association of the two organisms is generally regarded as a form
of symbiosis.
Eighty-two years ago Link observed fungi in the seedling
protocorm of an orchid, Goodyera procera, but he did not realise
that the substance was fungoid. It was not until seven years
afterwards, in 1847, that Reissik recognised fungi in the roots
of orchids and other plants.
I do not propose to give a historical resume of the progress
of knowledge respecting the fungus-root, as the literature of the
subject up to so recent a date as 1922 is cited in an article,
entitled "Orchid Mycorrhiza,"1 by J. Ramsbottom. Although
this article treats particularly of orchid fungus-root the references
are not restricted entirely to papers concerning these plants.
It will be, however, convenient to note the three Periods in the
study of the fungus-root as recognised by Gallaud.2 They
are:—
First Period 1840-1885. Very little detailed work was
described at this early stage. Writers recorded the fact that
fungi were in several instances found closely related to the
roots of various plants.
Second Period 1885-1894. It was during the first year
of this period that A. B. Franks made known the results of his
researches on the fungus-root. He introduced the term mycorr-
hiza to describe it, and he further differentiated two forms of
mycorrhiza. In one the fungus threads penetrate below the
epidermal tissues and enter the cells of the root to which they
attach themselves, in the other, the hyphae form a mantle around
the root. The first form he designated as endotropic mycor-
rhiza, the latter as ectotropic mycorrhiza. These two forms
are not distinctly separate, for it is now known that in the second
1. Ramsbottom, J., "Orchil Mycorrhiza." Brit. Myc. Soc., vol. viii., pp. 28-60, 1922.
2. Gallaud, F., "Etudes sur les mycorrhizes endotropes." Rev. Gen. Bot., xvii., pp. 5 et
passim, 1905.
3. Frank, A. B., "Ueber die auf Wurzelsymbiose beruhende Ernahrung gewisser Baume
durch unterirdische Pilze." Ber. d. deutsch. bot. Gesell, pp. 128-145, 1885.