A, B, D, F, G, H, I. _Lepidophloios_. (Fig. A should be reversed.) C, E. _Lepidodendron aculeatum_. A, B. From a specimen in the Sedgwick Museum, Cambridge (leaf-cushion 3 cm. broad). C. From a specimen in the Sedgwick Museum, Cambridge (leaf-cushion 4 cm. long). D. From a section in the Cambridge Botany School Collection. E. From a specimen in the Bunbury Collection, Cambridge Botany School, showing _Spirorbis_ shells (leaf-cushion 2 cm. long). F. From a section in the Williamson Collection, British Museum No. 1, 973. G, H, I. From sections in the Cambridge Botany School Collection.] Another feature worthy of notice in reference to the leaf-cushions of _Lepidodendron_ is the occurrence in rare instances of alternate zones of larger and smaller cushions. This variation in the size of the leaf-cushions is by no means uncommon in the closely allied genus _Sigillaria_; in _Lepidodendron_ it has been described by Potonié[252] in _L. volkmannianum_ and more recently by Mr Leslie and myself[253] in a South African species _L. vereenigense_. Owing to the natural exfoliation of the superficial layers of the outer bark at a certain stage in the growth of the plant, or in some instances no doubt as the result of _post-mortem_ decay, which destroys the delicate cells of the meristematic zone in the outer cortex, isolated leaf-cushions and strips of the external surface are occasionally met with as carbonised impressions. The appearance presented by a Lepidodendron stem which has been deprived of its superficial tissues may be dealt with more intelligibly after we have become familiar with the anatomical characters. iii. _Lepidophloios_. Before proceeding further with the genus _Lepidodendron_ a short account may be intercalated of the external features of a lepidodendroid type of stem which it is customary to describe under a distinct generic title _Lepidophloios_. This name is convenient for diagnostic purposes though it seems clear that apart from the form of the leaf-cushion (fig. 146, A) we are at present unable to recognise any well-defined differences between the two forms _Lepidodendron_ and _Lepidophloios_. For general purposes the name _Lepidodendron_ will be used as including plants possessing leaf-cushions of the type already described as well as those with the Lepidophloios form of cushion.