The _Parmeliae_ are mostly provided with abundant rhizinae; in _Cetrariae_ and _Nephromopsis_ these are very sparingly present, while in _Anzia_ (including _Pannoparmelia_) the medulla passes into a wide net-like structure of anastomosing hyphae. In _Heterodea_, cyphellae occur on the under surface as in Stictaceae; and in _Cetraria islandica_ bare patches have been described as pseudocyphellae. The latter lichen is one of the few that are of value as human food. Special aeration structures are present on the upper cortex of _Parmelia aspidota_. Thallus non-corticate below. Apothecia terminal 1. *Heterodea Nyl. Apothecia superficial 2. *Physcidia Tuck. Thallus spongy below 3. *Anzia Stizenb. Thallus corticate below. Asci poly-spored 4. Candelaria Massal. Asci 8-spored. Spermatia acrogenous 5. Parmeliopsis Nyl. Spermatia pleurogenous. Apothecia superficial 6. Parmelia Ach. Apothecia lateral. Apothecia on upper surface 7. Cetraria Ach. Apothecia on lower surface 8. *Nephromopsis Müll.-Arg. XLVII. _USNEACEAE_ This also is a familiar family of lichens, _Usnea barbata_ the “bearded moss” being one of the first lichens noted and chronicled. Algal cells Protococcaceae. Structure radiate, the upright or pendulous habit characteristic of the family securing all-round illumination. Special adaptations of the cortex or of the internal tissues have been evolved to strengthen the thallus against the strains incidental to their habit of growth as they are attached in nearly all cases by one point only, by a special sheath, or by penetrating hold-fasts. Apothecia are superficial or marginal and sometimes shortly stalked; spores are simple or variously septate. _Ramalina_ and _Usnea_, the most numerous, are cosmopolitan genera; _Alectoria_ inhabits northern or hilly regions. The genus _Evernia_, also cosmopolitan, represents a transition between foliose and fruticose types; the fronds of the two species, though strap-shaped and generally upright, are dorsiventral and stratose, the gonidia for the most part lying beneath one surface; the other (lower) surface is either white or very dark-coloured. _Everniopsis_, formed of thin branching strap-shaped fronds, is also dorsiventral.