An extraordinary development of the under cortex characterizes the genera _Anzia_[1011] and _Pannoparmelia_: rhizinae-like strands formed from the cortical cells branch and anastomose with others till a wide mesh of a spongy nature is formed. They are mostly tropical or subtropical or Australasian, and possibly the spongy mass may be of service in retaining moisture. A species of _Anzia_ has been recorded by Darbishire[1012] from Tierra del Fuego. _dd._ _USNEACEAE._ As we have seen, the change to fruticose structure has arisen as an ultimate development in a number of groups; it reaches however its highest and most varied form in this family. Not only are there strap-shaped thalli, but a new form, the filamentous and pendulous, appears; it attains to a great length, and is fitted to withstand severe strain. The various adaptations of structure in these two types of thallus have already been described[1013]. In _Parmelia_ itself there are indications of this line of development in _P. stygia_, with short stiff upright branching fronds, and in _P. pubescens_, with its tufts of filaments, but these two species are more or less dorsiventral in structure and do not rise from the substratum. In _Cetraria_ also there is a tendency towards upright growth and in _C. aculeata_ even to radiate structure. But advance in these directions has stopped short, the true line of evolution passing through species like _Parmelia physodes_ with raised, and in some varieties, tubular fronds, and the somewhat similar species _P. Kamtschadalis_ with straggling strap-like lobes, to _Evernia_. That genus is a true link between foliose and fruticose forms and has been classified now with one series, now with the other. In _Evernia furfuracea_, the lobes are free from the substratum except when friction causes the development of a hold-fast and the branching out of new lobes from that point. It is however dorsiventral in structure, the under surface is black and the gonidial zone lies under the upper cortex. _Evernia prunastri_ is white below and is more fruticose in habit, the long fronds all rising from one base. They are thin and limp, no strengthening tissue has been evolved, and they tend to lie over on one side; both surfaces are corticate and gonidia sometimes travel round the edge, becoming frequently lodged here and there along the under side. The extreme of strap-shaped fruticose development is reached in the genus _Ramalina_. In less advanced species such as _R. evernioides_ there is a thin flat expansion anchored to the substratum at one point and alike on both surfaces. In _R. fraxinea_ the fronds may reach considerable width (var. _ampliata_), but in that and in most species there is a provision of sclerotic strands to support and strengthen the fronds. One of those best fitted to resist bending strains is _R. scopulorum_ (_siliquosa_) which grows by preference on sea-cliffs and safely withstands the maximum of exposure to wind or weather.