The relation between the roots of plants and fungi.

Abstract

The relation of the roots of plants to the fungi in the soil forming a true symbiosis, is of importance not only in botany from the light it throws on some forms of plant nutrition, but in medicine also from the close relation between symbiosis and parasitism.

The roots of all annual plants and many others are closely related to the soil surfaces by fine hollow processes given off from the epidermic cells termed root hairs. While the leaves of the plant through the chlorophyl are the agents of production of the carbohydrates, the roots furnish the nitrogenous compounds and salts and the enormous amount of water which the plant requires. The roots of many of the shrubs and forest trees either have no root hairs or these are but slightly developed. This is especially the case in all of the ericaceæ and in most of the forest trees. The ericaceæ have very fine roots extending widely in the soil particularly in the surface humus.

The fine roots are accompanied by fungus hyphæ which extend upon the surface of the root, often forming a close surrounding mycelium, and certain of the hyphæ penetrate. The hyphæ on the surface are termed epitrophic and those penetrating endotrophic, but there is no sharp separation, both types being found in most plants. Some of these penetrating hyphæ extend along just beneath the epidermis, here and there sending short processes into the cells. The main cell invasion takes place from the hyphæ on the surface which sends fine haustoria into the epidermic cells, which by their extension and branching completely fill up the cells.

Much interest has been found in following the seasonal variation of the fungus relations.