Immediately above the centre of the upper boundary of a Sigillarian leaf-scar a ligule pit may often be detected, as shown in fig. 195, _l_, and in some cases, e.g. a specimen figured by Germar[463] (fig. 196, A) as _Sigillaria spinulosa_ (identical with _S. Brardi_), some circular scars with a central pit surrounded by a raised rim occur on the surface of the stem, either singly or in pairs, near the leaf-scars; these, it is suggested, may represent the position of adventitious roots or, as Germar thought, of some deciduous spinous processes. The leaf-scars are frequently hexagonal in shape, with the lateral angles either rounded (fig. 200, F) or sharply pointed (fig. 200, G, H); each scar bears three smaller scars as in _Lepidodendron_, a central circular, oval or crescentic leaf-trace scar and larger oval or slightly curved scars formed by the two parichnos arms (fig. 195, _p_). The larger size of the parichnos arms, the individual cells of which may often be detected as a fine punctation, is a distinguishing feature of the genus, but otherwise the structure is very similar to that in _Lepidodendron_. As shown in figs. 195, 200, F, G, the three scars may occur nearer the upper than the lower margin of the leaf-base area. _Lepidodendron Wortheni_[464] (fig. 196, E), described from North America by Lesquereux[465], by Zeiller[466] from France, and by Kidston[467] from the Upper and Middle Coal-Measures of England, may be quoted as a _Lepidodendron_ bearing a close resemblance to _Sigillaria_. The shoots bear cushions two or three times as long as broad and without the usual median division, but with numerous irregular and discontinuous transverse wrinklings. _Lepidodendron Peachii_ Kidston[468] affords another example of a form agreeing both with _Sigillaria_ and with _Lepidodendron_. An Upper Devonian type described by White[469] as _Archaeosigillaria primaeva_ affords a striking instance of the combination on one stem of Sigillarian and Lepidodendroid leaf-cushions. The difference between the original surface of a Sigillaria stem and that of partially decorticated specimens is seen in figs. 196, C and D; in fig. C the bark of _Sigillaria Brardi_ shows the characteristic wrinklings of the superficial tissue, while at a slightly lower level the leaf-scars are replaced by the parichnos casts, a, and fine longitudinal striations represent the elongated phelloderm cells laid bare by the exfoliation of the surface-layers. Similarly, in the rib of _Sigillaria laevigata_ (fig. 196, D) the parichnos arms, _p_, and the longitudinal striations are exposed at the lower level, while the surface is smooth and bears rows of widely separated leaf-scars. [Illustration: FIG. 197. _Carica sp._ From the Royal Gardens, Kew. (Much reduced.) M.S.]