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 algæ. 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 algæ, 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 algæ 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 algæ, whilst the second had that of fungi; 3rd. That the different forms and varieties of gonidia corresponded with parallel types of algæ; 4th. That as the germination of the spore had not been followed further than the development of a hypothallus, it might be accounted for by the absence of the essential algal on which the new organism should become parasitic; 5th. That there is a striking correspondence between the development of the fruit in lichens and in some of the sporidiiferous fungi (_Pyrenomycetes_).