The nests are usually below the surface of the soil, but covered, wherever necessary, with a thick mass of withered pieces of leaves and twigs, etc. They may be as much as 1-1/2 metres in diameter. In the nests of all species examined there is found, filling up the interior, a curious grey spongy mass, full of chambers, like a coarse sponge, in which the ants may be seen running about, and in which, here and there, occur eggs, larvae, and pupae. This is the fungus garden. It is separated from the roof and lateral walls of the nest by a clear space. The walls and roof are much thicker in winter than in summer; one nest examined had a roof 25 cm. thick and wall 40 cm. The garden consists of two parts, differently coloured, but not very sharply marked off from each other. The older part is yellowish-red in colour; the newly-built portions, forming the surface of the garden, are of a blue-black colour. It is this part which is of the greater importance to the ants. The garden is found, on examination, to consist of an immense conglomeration of small round particles of not more than .5 mm. in diameter, of a dark green colour when quite fresh, then blue-black, and finally yellowish-red. They are penetrated by, and enveloped in, white fungus hyphae, which hold the particles together. These hyphae are similar throughout the nest. Strewn thickly upon the surface of the garden are seen round white bodies about .25 mm. in diameter; they always occur in the nests, except in the very young portion of the gardens. They consist of aggregations of peculiar swollen hyphae, and are termed by Moeller the "Kohl-rabi clumps." The hyphae swell out at the ends into large spherical thickenings, filled with richly vacuolated protoplasm like the ordinary hyphae. These clumps of "Kohl-rabi" are only found on the surface of the garden, and form the principal food of the ants; they have no doubt reached their present form under the cultivation and selection of the ants. The fungus was found to belong to the genus _Rozites_, and the species was named _R. gongylophora_. A microscopic examination of the particles of which the garden is composed shows that they contain remains of leaves; bits of epidermis, stomata, spiral vessels, etc., occur in them. If a nest is broken into and the fungus garden scattered, the ants collect it as quickly as possible, especially the younger parts, taking as much trouble over it as over the larvae. They also cover it up again as soon as possible to protect it from the light. A nest, 1 metre x 50 cm., was opened, and in twenty-four hours the ants had put on a new roof 10 cm. deep.