The _Tuberacei_[D] are remarkable amongst the fungi in being all of them more or less hypogeous. They are natives of warm countries, and are distributed into numerous genera and species. The _Tuberacei_ constitute in Northern latitudes a group of fungi very poor in specific forms. The few species of the _Hymenogastres_ belonging to Sweden, with the exception of _Hyperrhiza variegata_ and one example of the genus _Octaviana_, are confined to the southern provinces. The greater part of this group, like the _Lycoperdacei_, are met with in the temperate zone. Most examples of the genus _Lycoperdon_ are cosmopolitan. The _Nidulariacei_ and the _Trichodermacei_ appear to be scattered over the globe in a uniform manner, although their species are not everywhere similar. The same statement applies to the _Myxogastres_, which are common in Lapland, and appear to have their central point of distribution in the countries within the temperate zone. At the same time, they are not wanting in tropical regions, notwithstanding that the intensity of heat, by drying up the mucilage which serves as the medium for the development of their spores, is opposed to their development.[E] Of the _Coniomycetes_, the parasitic species, as the _Cæomacei_, the _Pucciniei_, and the _Ustilagines_, accompany their foster-plants into almost all regions where they are found; so that smut, rust, and mildew are as common on wheat and barley in the Himalayas and in New Zealand as in Europe and America. _Ravenelia_ and _Cronartium_ only occur in the warmer parts of the temperate zone, whilst _Sartvellia_ is confined to Surinam. Species of _Podisoma_ and _Roestelia_ are as common in the United States as in Europe, and the latter appears also at the Cape and Ceylon. Wherever species of _Sphæria_ occur there the _Sphæronemei_ are found, but they do not appear, according to our present knowledge, to be so plentiful in tropical as in temperate countries. The _Torulacei_ and its allies are widely diffused, and probably occur to a considerable extent in tropical countries.