Cephalodia are developed on the primary thallus of _Pilophorus_, and on the podetia of _Stereocaulon_ and _Argopsis_. Podetia simple, short, not widening upwards. Podetial stalks naked. Primary thallus thin, continuous 1. Gomphillus Nyl. Primary thallus granular or squamulose 2. Baeomyces Pers. Primary thallus foliose. Podetia superficial 3. *Heteromyces Müll.-Arg. Podetia marginal 4. *Gymnoderma[1051] Nyl. Podetial stalks granular, squamulose 5. Pilophorus Th. Fr. Podetia short, widening upwards. Podetia simple above, rarely divided 6. *Glossodium Nyl. Podetia lobed, leaf-like 7. *Thysanothecium Berk. & Mont. Podetia elongate, variously branched, or scyphous and hollow 8. Cladonia Hill. Podetia elongate, not scyphous, the stalks solid. Spores elongate, septate 9. Stereocaulon Schreb. Spores muriform 10. *Argopsis Th. Fr. XXXIV. _GYROPHORACEAE_ A small family of foliose lichens allied to Lecideaceae by the character of the fruit—a superficial apothecium in the formation of which the gonidia take no share. There are only three genera, distinguished by differences in spore and other characters. _Dermatiscum_ has light-coloured thallus and fruits; of the two species, one occurs in Central Europe, the other in North America. _Umbilicaria_ and _Gyrophora_ are British; they are dark-coloured rock-lichens and are extremely abundant in Northern regions where they are known as “tripe de roche.” Algal cells Protococcaceae. _Umbilicaria_, _Dermatiscum_, and some species of _Gyrophora_ are attached to the substratum by a central point. Other species of _Gyrophora_ are rhizinose. In all there is a cortex of plectenchyma above and below. In _Gyrophora_ the thallus may be monophyllous as in _Umbilicaria_, or polyphyllous and with or without rhizinae. New lobes frequently arise from protuberances or warts on the older parts of the thallus. At the periphery, in most species, growth is equal along the margins, in _G. erosa_[1052] the edge is formed of numerous anastomosing lobes with lateral branching, the whole forming a broadly meshed open network. Further back the tissues become continuous owing to the active growth of the lower tissue or hypothallus, which grows out from all sides and meets across the opening. The overlying layers, with gonidia, follow more slowly, but they also in time become continuous, so that the “erose” character persists only near the periphery. This forward growth of the lower thallus occurs in other species, though to a much less marked degree.