s under
alliances in his "Vegetable Kingdom;" but, beyond this, there was no
predisposition towards the theory since propounded, and which, like
all new theories, has collected a small but zealous circle of
adherents. It will be necessary briefly to summarize this theory and
the arguments by which it is supported and opposed, inasmuch as it is
intimately connected with our subject.

As recently as 1868, Professor Schwendener first propounded his
views,[J] and then briefly and vaguely, that all and every individual
lichen was but an algal, which had collected about it a parasitic
fungal growth, and that those peculiar bodies which, under the name of
_gonidia_, were considered as special organs of lichens, were only
imprisoned algae. In language which the Rev. J. M. Crombie[K] describes
as "pictorial," this author gave the general conclusion at which he
had arrived, as follows:--"As the result of my researches, all these
growths are not simple plants, not individuals in the usual sense of
the term; they are rather colonies, which consist of hundreds and
thousands of individuals, of which, however, only one acts as master,
while the others, in perpetual captivity, provide nourishment for
themselves and their master. This master is a fungus of the order
_Ascomycetes_, a parasite which is accustomed to live upon the work of
others; its slaves are green algae, which it has sought out, or indeed
caught hold of, and forced into its service. It surrounds them, as a
spider does its prey, with a fibrous net of narrow meshes, which is
gradually converted into an impenetrable covering. While, however, the
spider sucks its prey and leaves it lying dead, the fungus incites the
algae taken in its net to more rapid activity; nay, to more vigorous
increase." This hypothesis, ushered upon the world with all the
prestige of the Professor's name, was not long in meeting with
adherents, and the cardinal points insisted upon were--1st. That the
generic relationship of the coloured "gonidia" to the colourless
filaments which compose the lichen thallus, had only been assumed, and
not proved; 2nd. That the membrane of the gonidia was chemically
different from the membrane of the other tissues, inasmuch as the
first had a reaction corresponding to that of algae, whilst the second
had that of fungi; 3rd. That the different forms and varieties of
gonidia corresponded with parallel types of algae; 4th. That as the
germination of the spore had not b