taria_ is confined
to the southern parts of South America and Tasmania. The United States
equal if they do not exceed European states in the number of species
of the _Discomycetes_. The _Phacidiacei_ are not confined to temperate
regions, but are more rare elsewhere. _Cordierites_ and _Acroseyphus_
(?) are tropical genera, the former extending upwards far into the
temperate zone, as _Hysterium_ and _Rhytisma_ descend into the
tropics. Amongst the _Sphaeriacei_, _Xylaria_ and _Hypoxylon_ are well
represented in the tropics, such species as _Xylaria hypoxylon_ and
_Xylaria corniformis_ being widely diffused. In West Africa an
American species of _Hypoxylon_ is amongst the very few specimens that
have ever reached us from the Congo, whilst _H. concentricum_ and
_Ustulina vulgaris_ seem to be almost cosmopolitan. _Torrubia_ and
_Nectria_ extend into the tropics, but are more plentiful in temperate
and sub-tropical countries. _Dothidea_ is well represented in the
tropics, whilst of the species of _Sphaeria_ proper, only the more
prominent have probably been secured by collectors; hence the
_Superficiales_ section is better represented than the _Obtectae_, and
the tropical representatives of foliicolous species are but few.
_Asterina_, _Micropeltis_, and _Pemphidium_ are more sub-tropical than
temperate forms. The _Perisporiacei_ are represented almost
everywhere; although species of _Erysiphe_ are confined to temperate
regions, the genus _Meliola_ occupies its place in warmer climes.
Finally, the _Tuberacei_, which are subterranean in their habits, are
limited in distribution, being confined to the temperate zone, never
extending far into the cold, and but poorly represented out of Europe.
One species of _Mylitta_ occurs in Australia, another in China, and
another in the Neilgherries of India; the genus _Paurocotylis_ is
found in New Zealand and Ceylon. It is said that a species of _Tuber_
is found in Himalayan regions, but in the United States, as well as in
Northern Europe, the _Tuberacei_ are rare.

The imperfect condition of our information concerning very many
countries, even of those partially explored, must render any estimate
or comparison of the floras of those countries most fragmentary and
imperfect. Recently, the mycology of our own islands has been more
closely investigated, and the result of many years' application on the
part of a few individuals has appeared in a record of some 2,809
species,[F] to which sub