This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Slender, ascending, simple or branched, 1°-2° high. Basal and lower leaves slender-petioled, 2-3-ternate, the segments ovate, oblong, or oval, mostly obtuse, 1/2'-1' long, sharply serrate; stem-leaves ternate, or biter-nate, short-petioled, or sessile, their segments lanceolate, generally narrower than those of the preceding species; rays of the umbel 2-12, slender, divergent, 1-3' long; fruit oval, or broader than long, about 1" long, often 1 1/4" wide.
Smyrnium cordatum Walt. Fl. Car. 114. 1788.
Zizia cordata DC. Prodr. 4: 100. 1830.
Thaspium trifoliatum var. apterum A. Gray, Man. Ed. 2, 156. 1856.
Stout, erect, branched, glabrous, or somewhat pubescent, 2°-3° high. Basal and lower leaves long-petioled, broadly ovate, or orbicular, undivided, deeply cordate at the base, sometimes 6' long, crenate all around; stem-leaves shorter-petioled, ter-nate, or rarely quinate, the segments ovate, or oval, crenate, or lobed; rays of the umbel 7-16, ascending, 1'-2' long; fruit ovate, or oval, about 1 1/2" long and 1" wide.
26. ÀPIUM [Tourn.] L. Sp. Pl. 264. 1753.
[Petroselinum Hoffm. Gen. Umb. 78, 177. 1814.]
Annual or biennial herbs, with 1-3-pinnate leaves, and yellow or yellowish flowers in compound umbels. Calyx-teeth obsolete. Stylopodium short-conic. Fruit ovate; carpels with 5 filiform ribs; oil-tubes solitary in the intervals, 2 on the commissural side. [Latin, parsley.]
A genus of 5 European species, the following typical.
Apium Petroselinum L. Sp. Pl. 264. 1753. Petroselinum hortense Hoffm. Gen. Umb.
163. 1814. Petroselinum sativum Hoffm. Gen. Umb.
177. 1814. Petroselinum Petroselinum Karst. Deutsch.
Fl. 831. 1882.
Erect, usually biennial, 1°-.3° high, much branched, glabrous. Leaves bi-pinnate, triangular in outline, the segments ovate, dentate, or incised, or those of the upper leaves linear-oblong and entire; umbels peduncled, 1-2 1/2 broad, axillary and terminal, 15-20-rayed; rays 5"-12" long; pedicels about 1 1/2" long; involucre of 2-4 linear bracts; bractlets of the involucels subulate; flowers greenish yellow; fruit ovate, glabrous, about 2" long, the ribs rather prominent when dry.
Maryland to Ontario, escaped from cultivation. Introduced from Europe. Native of the Mediterranean region. Leaves of some cultivated races crisped. Summer.