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gonidia grew out of the rest of the thallus, but that such connexion 
as he had seen and described between these various parts of a 
Lichen, might be better explained as a parasitism of a fungus upon 
an alga. His new view he embodied in a small work that he 
published in 1869. The theory at once aroused great attention 
among botanists, and it was discussed from various standpoints. 
From that day to this the dispute has gone on, and, though 
lichenologists still oppose the theory as contrary to many certain 
facts, it has latterly obtained a large number of adherents, chiefly 
owing to its acceptance by Sachs, whose text-book on Botany is so 
generally used and admired; and perhaps it may be true to say 
that the advocates of the hypothesis are at the present time in the 
majority. 
But the theory now accepted is a modification of that originally 
proposed. As now explained, it is much more plausible than the 
crude view Schwendener enunciated at first. The assertion that 
the clear cells of a Lichen, or what he called the fungus, preyed 
upon and destroyed the green cells, was too contrary to every-day 
experience to be long persisted in. Some advocates of the theory 
present it now in another guise, and assert that each Lichen is 
made up of two plants differing in origin and nature, and belonging 
indeed to quite distinct classes, which lead together a mutually 
dependent life. The clear cells, they say, form the body of a 
fungus which is unable of itself to assimilate carbonic-oxide, and 
therefore lives on the waste products of the green cells or alge, 
which in turn benefit so greatly from the shelter afforded by the 
fungus, that it is doubtful whether they could in some instances 
live without it. 
To consider all the vos and cons of the argument, which already 
has given rise to a considerable literature of its own, is quite 
impossible now. I shall only say that I do not yet see my way to 
accept it even so far as to admit that there are two plants in each 
Lichen ; while all the facts that I have been able to glean respecting 
the morphology of Fungi are quite inconsistent with what I know 
to be the case in Lichens. Even if it could be proved that the 
green cells are no part of the Lichen—that is, of the plant whose 
