A family of about 466 genera and about 3820 species of herbs (rarely shrubs or trees), cosmopolitan, but especially north temperate (Plunkett et al. 2018). Hydrocotyle is more closely related to Araliaceae, and has been transferred there (Chandler & Plunkett 2004; Plunkett et al. 2018).
ID notes: The Apiaceae is an easy family to recognize (with some exceptions). These are herbs, typically with a clasping petiole base and often a variously (and often highly) compound leaf, either 1-5× pinnately, palmately, pinnately-ternately, or ternately compound (less commonly simple or phyllodial). The inflorescence is typically a simple or compound umbel (sometimes subcapitate or truly modified into a head) with numerous small flowers. Subtending the inflorescence is (usually) an involucre of individual bracts. If the umbel is compound, rays support umbellets, each of which may be subtended by an involucel of individual bractlets. The ovary is 2-carpellate, with 2 styles at the summit, these often swollen at the base into a stylopodium capping the ovary. The fruit develops into 2 mericarps, united by their faces at the commissure; each mericarp may be terete, flattened dorsally (parallel to the commissure, the commissure therefore broad), or flattened laterally (perpendicular to the commissure, the commissure therefore narrow). Each mericarp has 5 primary ribs, one down the back (the dorsal rib), 2 near each edge near the commissure (the lateral ribs or lateral wings), and 2 in-between (the intermediate ribs). The ribs may be thin and filiform in ×-section, corky, or winged, and they (or the entire outer surface of the mericarp) may also be ornamented with hairs, spines, uncinate prickles, etc.