Key to the common families

Hsuan Keng : Malayan seed plants

A.	Ovules and seeds generally naked, borne on the margins of a carpel (or megasporophyll) or on the surface of a scale, rarely, enveloped by a perianth-like sheath.	I.Gymnospermae
A.	Ovules enclosed in an ovary which is formed by the infolded lower portion of the carpel or united carpels.	II.Angiospermae

B.	Embryo with two cotyledons; vascular bundles usually arranged in a cylinder in the stem and generally showing secondary increase in thickness; leaves usually net-veined; flowers frequently four-or five-merous.	IIa.Dicotyledoneae
B.	Embryo with a single cotyledon, rarely, undifferentiated; vascular bundles scattered in the stem, and rarely, showing secondary increase in thickness; leaves usually parallel-veined; rarely, net-veined; flowers usually three-merous.	IIb.Monocotyledoneae

II a. Dicotyledoneae

1.	Calyx and corolla both present, usually forming two different series (sometimes perianth segments nearly alike, but in two or more whorls.)
	2.	Petals (or the inner perianth-segments) separate or nearly so, normally falling away individually when shed.
		3.	Ovary superior
			4.	Stamens numerous, more than twice as many as the petals.	A.
			4.	Stamens definite, not more than twice as many as the peatas.	B.
		3.	Ovary inferior or half-inferior.
			4.	Stamens numerous, more than twice as the petals.	C.
			4.	Stamens definite, not more than twice as many as the petal	D.
	2.	Petals more or less united, the corolla usually falling away as a whole when shed.
		3.	Ovary superior		E.
		3.	Ovary inferior or half-inferior		F.
1.	Corolla absent, or the perianth segments all alike (usually in one whorl), or the perianth entirely wanting.				G.