In the brown-spored series there is a considerable number of species that are crustaceous united in the genus _Rinodina_, all of which have marginate apothecia. One of them, _Rinodina oreina_, approaches in thalline structure the effigurate forms of _Placodium_; while in _R. isidioides_, a rare British species, there is an isidioid squamulose development. Among foliose genera, the tropical genus _Pyxine_ is peculiar in its almost lecideine fruit, a few gonidia occurring only in the early stages; its affinity with _Physcia_ holds, however, through the one-septate brown spores with very thick walls and the reduced lumen of the cells. The more simple type of fruit may be merely retrogressive. _Physcia_, the remaining genus, is mainly foliose and with dorsiventral thallus. A few species have straggling semi-upright fronds and these have sometimes been placed in a separate genus _Anaptychia_. Only one “_Anaptychia_,” _Ph. intricata_, has a radiate structure with fibrous cortex all round; in the others the upper cortex alone is fibrous—of long parallel hyphae—but that character appears in nearly every one of the horizontal species as well, sometimes in the upper, sometimes in the lower cortex. In _Physcia_ the horizontal thallus is of smaller dimensions than in _Parmelia_, and never becomes so free from the substratum: it is attached by rhizinae and soredia appear frequently. Very often the circular effigurate type of development prevails. It is difficult to trace with any certainty the origin of this series of the phylum. Some workers have associated it with the purely lecideine genus, _Buellia_, but the brown septate spores of the latter are of simple structure, though occasionally approaching the _Rinodina_ type. There are also differences in the thallus, that of _Buellia_, especially when it is saxicolous, inclining to _Rhizocarpon_ in form. It is more consistent with the outer and inner structure to derive Rinodina from some crustaceous _Placodium_ form with a marginate apothecium, therefore from a form of fairly advanced development. As the parietin content disappeared—perhaps from the preponderance of other acids—the colouration changed and the spores became dark-coloured. Many genera and even families, such as Thelotremaceae, etc., have necessarily been omitted from this survey of phylogeny in lichens, but the tracing of the main lines of development has indicated the course of evolution, and has demonstrated not only the close affinity between the members of this polyphyletic class of plants, as shown in the constantly recurring thalline types, but it has proved the extraordinary vigour gained by both the component organisms through the symbiotic association. The principal phyla[1015], developing on somewhat parallel lines, are given in the appended table: ARCHILICHENS