Pinus: Answers to key questions leading to this genus. 

	Needles on year-old and older branches borne either in groups (fascicles) of 2 with each fascicle scaly-sheathed at base at least when young, or in clusters of 12-25 on short shoots with clusters not scaly sheathed.  NOT [Needles borne singly along branches, not in fascicles scaly-sheathed at base or on short shoots.]
	Needles in clusters of 12-25 on short shoots, deciduous; scales of seed cones without apophyses, umbos, and prickle.  NOT [Needles in fascicles of 2 on dwarf shoots, evergreen; scales of seed cones with thickened apical portion (apophysis) bearing terminal or central, scar-like to raised umbo and often a prickle or hook.]

Pinaceae: Answers to key questions leading to this family. 

Leaves needle-like, alternate or fascicled/clustered, shed individually from branchlets (usually shed as fascicles in Pinus); seed cone scales imbricate; seed cones dry; seeds adaxial and 2 per scale.  NOT [Leaves needle-like or scale-like, alternate, opposite or whorled, persistent on shoots, shedding with branchlets with age; seed cone scales fused or imbricate; seed cones berry-like (Juniperus) or dry (Thuja); seeds adaxial or terminal and 1-20 per scale.]