Compare, for instance, the cross-section of a pine needle with that of a grass or maple. Others are morphological and easily seen. Some leaves have stipules at the base of the petiole. Leaves with a single blade are said to be simple . In compound leaves , there are several leaflets , i.e., distinct parts of the blade.
Most grasses have a ligule at the junction of the leaf sheath and leaf blade.
In some grasses it consists of hairs. The Selaginellales and Isoetales have a small ligule in the leaf axils. The kind of leaf found in true ferns, gymnosperms, and angiosperms. Often, but not always, large in size. Some megaphyllous leaves appear to have only a single, unbranched vein but a study of their anatomy shows that they are, basically megaphyllous leaves in which the complexity of the venation has been reduced over that which was present in the species' ancestors.