paratively permanent, that
is, that they should constitute good species. Here, also, efforts have
been made to develop a theory that there are no legitimate species
amongst fungi, accepting the terms as hitherto applied to flowering
plants. In this, as in allied instances, too hasty generalizations
have been based on a few isolated facts, without due comprehension of
the true interpretation of such facts and phenomena. Polymorphism will
hereafter receive special illustration, but meantime it may be well to
state that, because some forms of fungi which have been described, and
which have borne distinct names as autonomous species, are now proved
to be only stages or conditions of other species, there is no reason
for concluding that no forms are autonomous, or that fungi which
appear and are developed in successive stages are not, in their
entirety, good species. Instead, therefore, of insinuating that there
are no good species, modern investigation tends rather to the
establishment of good species, and the elimination of those that are
spurious. It is chiefly amongst the microscopic species that
polymorphism has been determined. In the larger and fleshy fungi
nothing has been discovered which can shake our faith in the species
described half a century, or more, ago. In the Agarics, for instance,
the forms seem to be as permanent and as distinct as in the flowering
plants. In fact, there is still no reason to dissent, except to a very
limited extent, from what was written before polymorphism was
accredited, that, "with a few exceptions only, it may without doubt be
asserted that more certain species do not exist in any part of the
organized world than amongst fungi. The same species constantly recur
in the same places, and if kinds not hitherto detected present
themselves, they are either such as are well known in other districts,
or species which have been overlooked, and which are found on better
experience to be widely diffused. There is nothing like chance about
their characters or growth."[F]

The parasitism of numerous minute species on living and growing plants
has its parallel even amongst phanerogams in the mistletoe and
broom-rape and similar species. Amongst fungi a large number are thus
parasitic, distorting, and in many cases ultimately destroying, their
host, burrowing within the tissues, and causing rust and smut in corn
and grasses, or even more destructive and injurious in such moulds as
those of the po