Corylus: Answers to key questions leading to this genus 

Fruit a nut over 1 cm long, enclosed in a tube-like involucre; bud scales and bracts of staminate catkins with coarse, straight, appressed hairs; pistillate catkins few-flowered and borne on short bud-like branches that are distal to the staminate catkins and visible primarily as reddish styles projecting from the bud at anthesis; NOT [Fruit a samara, much shorter than 1 cm and subtended by a flat scale; bud scales and bracts of staminate catkins not coarsely hairy; pistillate catkins many-flowered, erect or pendulous, often borne on short shoots proximal to the staminate catkins.]

Betulaceae: Answers to key questions leading to this family. 

	Plants monoecious or dioecious, fruits 1-seeded samaras, nuts or drupes; NOT [Plants dioecious; fruits many-seeded capsules]
	Plants monoecious; fruits samaras or nuts lacking waxy protuberances and persistent bracts and bracteoles; plant not aromatic; leaf glands, if present, resinous and not as above; NOT [Plants usually dioecious; fruit a nut or drupe, often covered with warty protuberances with waxy coating or sometimes enclosed by persistent, accrescent bracts and bracteoles; plants usually aromatic; leaves commonly with peltate, multicellular, glandular trichomes]
	Fruits samaras or nuts, if nuts, then lacking a cupule but sometimes subtended or enclosed by a foliaceous hull developed from 2-3 bracts; NOT [Fruits nuts surrounded or partly surrounded by a cupule; this fruit is the acorn of oaks]