ed those
grains wherever they have been distributed, and the potato disease,
which is said to have been known in the native region of the potato
plant before it made its appearance in Europe. We might also allude to
_Puccinia malvacearum_, Ca., which was first made known as a South
American species; it then travelled to Australia, and at length to
Europe, reaching England the next year after it was recorded on the
Continent. In the same manner, so far as we have the means of knowing,
_Puccinia Apii_, Ca., was known on the Continent of Europe for some
time before it was detected on the celery plants in this country.
Experience seems to warrant the conclusion that if a parasite affects
a certain plant within a definite area, it will extend in time beyond
that area to other countries where the foster-plant is found. This
view accounts in some part for the discovery of species in this
country, year after year, which had not been recorded before; some
allowance being made for the fact that an increased number of
observers and collectors may cause the search to be more complete, yet
it must be conceded that the migration of Continental species must to
some extent be going on, or how can it be accounted for that such
large and attractive fungi as _Sparassis crispa_, _Helvellas gigas_,
and _Morchella crassipes_ had never been recorded till recently, or
amongst parasitic species such as the two species of _Puccinia_ above
named? In the same manner it is undoubtedly true that species which at
one time were common gradually become somewhat rare, and at length
nearly extinct. We have observed this to apply to the larger species
as well as to the microscopic in definite localities. For instance,
_Craterellus cornucopioides_ some ten years ago appeared in one wood,
at a certain spot, by hundreds, whereas during the past three or four
years we have failed to find a single specimen. As many years since,
and in two places, where the goat's-beard was abundant, as it is now,
we found nearly half the flowering heads infested with _Ustilago
receptaculorum_, but for the past two or three years, although we have
sought it industriously, not a single specimen could be found. It is
certain that plants found by Dickson, Bolton, and Sowerby, have not
been detected since, whilst it is not improbable that species common
with us may be very rare fifty years hence. In this manner it would
really appear that fungi are much more liable than flowering pl