imple spored rust first makes its appearance, and
later the bilocular "mildew." It is by no means uncommon to find the
two forms in the same pustule. Some have held, without good reason,
that the simple cells became afterwards divided and converted into
_Puccinia_, but this is not the case; the uredo-spores are always
simple, and remain so except in _Uredo linearis_, where every
intermediate stage has been observed. Both are also perfect in their
kind, and capable of germination.

What the precise relations between the two forms may be has as yet
never been revealed to observers, but that the two forms belong to one
species is not now doubted. Very many species of _Puccinia_ have
already been found associated with a corresponding _Trichobasis_, and
of _Phragmidium_ with a relative _Lecythea_, but it may be open to
grave doubt whether some of the very many species associated by
authors are not so classed upon suspicion rather than observation. We
are ready to admit that the evidence is strong in favour of the
dimorphism of a large number of species--it _may_ be in all, but this
awaits proof, or substantial presumption on good grounds. Up to the
present we know that there are species of _Trichobasis_ which have
never been traced to association with a _Puccinia_, and doubtless
there will be species of _Puccinia_ for which no corresponding _Uredo_
or _Trichobasis_ can be found.

Tulasne remarks, in reference to _Puccinia sonchi_, in one of his
memoirs, that this curious species exhibits, in effect, that a
_Puccinia_ may unite three sorts of reproductive bodies, which, taking
part, constitute for the mycologists of the day three entirely
different plants--a _Trichobasis_, a _Uromyces_, and a _Puccinia_. The
Uredines are not less rich, he adds, in reproductive bodies of divers
sorts than the _Pyrenomycetes_ and the _Discomycetes_; and we should
not be surprised at this, since it seems to be a law, almost constant
in the general harmony of nature, that the smaller the organized
beings are, the more their races are prolific.

In _Puccinia variabilis_, Grev., it is common to find a unicellular
form, species of _Trichobasis_, in the same pustules. A like
circumstance occurs with _Puccinia violarum_, Link., and _Trichobasis
violarum_, B.; with _Puccinia fallens_, C., and _Trichobasis fallens_,
Desm.; also with _Puccinia menthae_, P., and _Trichobasis Labiatarum_,
D. C. In _Melampsora_, again, the prismatic pseudospores of
_Mel