_c._ GRAPHIDINEAE. This series contains a considerable variety of lichen forms, but all possess to a more or less marked degree the linear form of fructification termed a “lirella” which has only a slit-like opening. There is a tendency to round discoid fruits in the _Roccellae_ and also in the _Arthoniae_; the apothecia of the latter, called by early lichenologists “ardellae,” are without margins. In nearly all there is a formation of carbonaceous black tissue either in the hypothecium or in the proper margins. In some of them the paraphyses are branched and dark at the tips, the branches interlocking to form a strong protective epithecium. There are, however, constant exceptions, in some particular, to any generalization in genera and in species. Müller-Argau’s[991] pronouncement might be held to have special reference to Graphidineae: “that in any genus, species or groups of species are to be found which outwardly shew something that is peculiar, though of slight importance.” The most constant type of gonidium is _Trentepohlia_, but _Palmella_ and _Phycopeltis_ occasionally occur. The spores are various in colour and form; they are rarely simple. The genus _Arthonia_ is derived from a member of the Patellariaceae, from which family many of the Discomycetes have arisen. The course of development does not follow from a closed to an open fruit; the apothecium is open from the first, and growth proceeds from the centre outwards, the fertile cells gradually pushing aside the sterile tissue of the exterior. The affinity of _Xylographa_ (with _Palmella_ gonidia) is to be found in _Stictis_ in the fungal family Stictidaceae, the apothecia of _Stictis_ being at first closed, then open, and with a thick margin; _Xylographa_ has a more elongate lirella fruit, though otherwise very similar, and has a very reduced thallus. Rehm[992] has classified _Xylographa_ as a fungus. The genera with linear apothecia are closely connected with Hysteriaceae, and evidently inherit their fruit form severally from that family. There is thus ample evidence of polyphyletic descent in the series. Stromatoid fruits occur in Chiodectonaceae, with deeply sunk, almost closed disc, but they have evidently evolved within the series, possibly from a dividing up of the lirellae. In Graphidineae there are also forms, more especially in Arthoniaceae, on the border line between lichens and fungi: those with gonidia being classified as lichens, those without gonidia having been placed in corresponding genera of fungi. These latter athalline species live as parasites or saprophytes. The larger number of genera have a poorly developed thallus; in many of them it is embedded within the outer periderm-cells of trees, and is known as “hypophloeodal.” But in some families, such as Roccellaceae, the thallus attains a very advanced form and a very high production of acids.