1.a. Leaves needle-like; in fasicles on short shoots.
1.b. Leaves flat or square in cross-section; not in fascicles.
2.a. Leaves evergreen, in fascicles of 2 or 4.
2.b. Leaves deciduous, numerous and crowded on short lateral shoots.
3.a. Leaves persistent on dry branches; twigs with round, flat leaf scars; resin blisters prominent on the trunks.
3.b. Leaves falling readily from dry branches; twigs rough with persistent peg-like leaf scars; trunks without prominent resin blisters.
4.a. Leaves flattened, rounded at apex, distinctly short-stalked on peg-like base.
4.b. Leaves square in cross-section, acute or sharp-pointed, sessile on peg-like base.