In _Blastenia_ the outer thalline margin is obscure or absent—though gonidia are frequently present below the hymenium. Caloplacaceae occur all over the globe; they are among the most brilliantly coloured of all lichens. _Polycauliona_ Hue[1060] possibly belongs here: though based on thalline rather than on spore characters, one species at least has polarilocular spores. Apothecia with a distinct thalline margin 1. Caloplaca Th. Fr. Apothecia without a thalline margin 2. Blastenia Th. Fr. XLIX. _TELOSCHISTACEAE_ Polarilocular colourless spores are the distinguishing feature of this family as of the Caloplacaceae. Algal cells Protococcaceae. The thallus of Teloschistaceae is more highly developed, being either foliose or fruticose, though never attaining to very large dimensions. The cortex of _Xanthoria_ (foliose) is plectenchymatous, that of _Teloschistes_ (fruticose) is fibrous. The species of both genera are yellow or greenish-yellow due to the presence of the lichen-acid parietin. Both genera have a wide distribution over the globe, more especially in maritime regions. Thallus foliose 1. Xanthoria Th. Fr. Thallus fruticose 2. Teloschistes Norm. L. _BUELLIACEAE_ A family of crustaceous lichens distinguished by the brown two-celled spores. Algal cells Protococcaceae. Zahlbruckner has included here _Buellia_ and _Rinodina_; the former with a distinctly lecideine fruit and with thinly septate spores; the latter lecanorine and with spores of the polarilocular type, with a very wide central septum pierced in most of the species by a canal which may or may not traverse the middle lamella of the wall. _Rinodina_ is closely allied to Physciaceae, while _Buellia_ has more affinity with Lecideaceae and is near to _Rhizocarpon_. Both genera are of world-wide distribution. Apothecia lecideine, without a thalline margin 1. Buellia De Not. Apothecia lecanorine, with a thalline margin 2. Rinodina Massal. LI. _PHYSCIACEAE_ Thallus foliose or partly fruticose, and generally attached by rhizinae. Algal cells Protococcaceae. The spores resemble those of _Rinodina_, dark-coloured with a thick septum and reduced cell-lumina. As in that species there may be a second septum in each cell, giving a 3-septate spore; but that is rare. _Pyxine_, a tropical or subtropical genus, is lecanorine only in the very early stages; it soon loses the thalline margin. _Anaptychia_ is differentiated from _Physcia_ by the subfruticose habit, though the species are nearly all dorsiventral in structure, only a few of them being truly radiate and corticate on both surfaces. The upper cortex of _Anaptychia_ is fibrous, but that character appears also in most species of _Physcia_ either on the upper or the lower side. _Physcia_ and _Anaptychia_ are widely distributed.