The shoot system of _Sigillaria_ consisted of a stout stem tapering upwards to a height of 100 feet[457] or more as an unbranched column, with its dome-shaped apex[458] covered with linear grass-like leaves or, in some species, such as _Sigillaria Brardi_[459], _S. Eugenii_[460], etc., the main trunk was occasionally divided by apparently equal dichotomy. The younger portions of the stem or branches were in some species clothed with leaves separated by a narrow zigzag groove surrounding their hexagonal bases, while in other forms each leaf was seated on a more or less prominent cushion having the form illustrated by _Sigillaria McMurtriei_ (fig. 194) or by the example represented in fig. 200, H; or as in the ribbed species shown in figs. 193, B, and 195, the leaves in vertical series were separated from one another by longer portions of the ribs. As in _Lepidodendron_ the cushions are frequently characterised by irregular transverse wrinklings and other[461] surface-ornamentation which in some instances at least may have been produced as the result of _post-mortem_ shrinkage of superficial tissue. From the rarity of shoots with the foliage attached, it would seem that the leaves persisted for a comparatively short time and were cut off by an absciss-layer leaving behind a well-marked leaf-scar area. The linear leaves, reaching in rare cases a length of one metre (e.g. _S. lepidodendrifolia_) but usually much shorter, possessed a single median bundle, and the lower face was characterised by two stomatal grooves and a median keel. It is not uncommon to find leaf-bases of _Sigillaria_ detached from the stem and preserved as separate impressions. The term _Sigillariophyllum_ used by Grand’Eury[462] may be applied to detached leaves, though it is by no means easy to distinguish between the foliage of _Sigillaria_ and _Lepidodendron_. A comparison of a typical species of _Sigillaria_, such as _S. rugosa_ (fig. 193, B) or _S. Brardi_ (fig. 196, A–C) with a typical _Lepidodendron_ reveals obvious differences in the form of the leaf-cushion, but in some cases the distinction becomes purely arbitrary. [Illustration: FIG. 194. _Sigillaria McMurtriei_ Kidst. From a specimen from the Upper Coal-Measures of Radstock, in the British Museum (V. 952). Nat. size.] [Illustration: FIG. 195. _Sigillaria mammillaris._ (Rhytidolepis form.) From a specimen in the Manchester Museum. _p_, parichnos; _l_, ligule-pit; _t_, leaf-trace; _c_, cushion; _s_, leaf-scar.] [Illustration: FIG. 196. A–C. _Sigillaria Brardi._ (A after Germar; B, C after Zeiller.) D. _Sigillaria laevigata._ E. _Lepidodendron Wortheni_ (D and E after Zeiller).]