Leaf shape is determined by leaf lying flat on a surface. As with the rest of the tool, botanical names have been avoided in lieu of more general terms. It is also worth noting that a number of the taxa included in this tool may have wide variability in leaf shape, often because the "leaves" are actually leaflets. The key is scored to accommodate this variability.
Linear leaves includes broad leaves that are generally long and narrow, with parallel sides and rounded ends. Note the contrast between needle-like leaves.
Scale-like leaves appear similar to scales; they may be very small and lie flat or they may be larger and protruding.
Needle-like leaves are quite narrow and generally pointed. This category generally applies to conifer needles.
Lance-shaped leaves are long and wider in the middle, generally pointed at both ends.
Elliptic or oval leaves are oval-shaped, with a small or no point at the tip. (Note that in the photograph, the left leaf is elliptic while the right one is lance-shaped. This is an example of a species that is highly variable in terms of leaf shape.)
Round leaves are circular in their overall form. There may be some tapering at either end of the leaf, but the general shape is circular.
Oblong leaves have an elongated form with parallel sides. This state is similar to linear leaves, but the leaf is broader and not as narrow. The ends are generally rounded, not tapered.
Egg-shaped leaves are broad at one end and narrow at the other, like an egg. The narrow end may be at the base or at the tip of the leaf.
Lobed leaves have deeply indented margins. They may be more shallowly indented, as in the illustration, or very deeply indented, as in the photograph.
Curled from drying leaves have curled so much from drying that their shape is no longer easily recognizable. Some leaves are particularly prone to this type of curling.
Some entities are so variable that they may fall into more than one of these categories. Feel free to choose mulitple states if this applies to your specimen; however, since the key is scored to accommodate variability, you may be able to key down more quickly if you choose one state.