the presence of different kinds
in the same substratum, and therefore the mixture not only of
different sorts of mycelia, but also that different kinds of spores
are sown. With some care and patience, these difficulties are in no
way insurmountable, and they must at any rate be overcome; the organic
continuity or non-continuity must be cleared up, unless the question
respecting the course of development, and the series of forms of
special kinds, be laid on one side as insolvable.

Simple and intelligible as these principles are, they have not always
been acted upon, but partly neglected, partly expressly rejected, not
because they were considered false, but because the difficulties of
their application were looked upon as insurmountable. Therefore
another method of examination was adopted; the spores of a certain
form were sown, and sooner or later they were looked after to see what
the seed had produced--not every single spore--but the seed _en
masse_, that is, in other words, what had grown on that place where
the seed had been sown. As far as it relates to those forms which are
so widely spread, and above all grow in conjunction with one
another--and that is always the case in the specimens of which we
speak--we can never be sure that the spores of the form which we mean
to test are not mingled with those of another species. He who has made
an attentive and minute examination of this kind knows that we may be
sure to find such a mixture, and that such an one was there can be
afterwards decidedly proved. From the seed which is sown, these
spores, for which the substratum was most suitable, will more easily
germinate, and their development will follow the more quickly. The
favoured germs will suppress the less favoured, and grow up at their
expense. The same relation exists between them as between the seeds,
germs, and seedlings of a sown summer plant, and the seeds which have
been undesignedly sown with it, only in a still more striking manner,
in consequence of the relatively quick development of the mildew
fungus.

Therefore, that from the latter a decided form, or a mixture of
several forms, is to be found sown on one spot, is no proof of
their generic connection with one which has been sown for the
purpose of experiments; and the matter will only be more confused
if we call imagination to our aid, and place the forms which are
found near one another, according to a real or fancied resemblance,
in a certain ser