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..
Herbs, with alternate decompound, compound or sometimes simple leaves, the petioles often dilated at the base, the stems often hollow. Stipules none, or rarely present and minute. Flowers small, white, yellow, greenish, blue or purple, generally in compound or simple umbels, rarely in heads or capitate clusters, often polygamous. Umbels and umbellets commonly involucrate or involucellate. Calyx-tube wholly adnate to the ovary, its margin truncate or 5-toothed, the teeth seldom conspicuous. Petals 5, inserted on the margin of the calyx, usually with an inflexed tip, often emarginate or 2-lobed, those of the outer flowers sometimes larger than those of the inner. Stamens 5, inserted on the epigynous disk; filaments filiform; anthers versatile. Ovary inferior, 2-celled; styles 2, filiform, distinct, straight or recurved after flowering, persistent, often borne on a conic or depressed stylopodium; ovules 1 in each cavity, pendulous, anatropous. Fruit dry, composed of 2 carpels (mericarps), which generally separate from each other at maturity along the plane of their contiguous faces (the commissure). Fruit either flattened laterally (at right angles to the commissure), or dorsally (parallel to the commissure), or nearly terete (not flattened). Carpels after parting from each other supported on the summit of a slender axis (the carpophore), each with 5 primary ribs in their pericarps (rarely ribless), and in some genera with 4 additional secondary ones, the ribs or some of them often winged. Pericarp membranous or corky-thickened, usually containing oil-tubes between the ribs, or under the ribs and on the commissural sides, sometimes irregularly scattered, sometimes none. Seeds 1 in each carpel, usually adnate to the pericarp, their inner faces flat or concave; seed-coat thin; endosperm cartilaginous; embryo small, placed near the hilum; cotyledons ovate, oblong or linear.
* Text prepared with the assistance of Dr. J. N. Rose.
About 250 genera and probably 2000 species, of wide geographic distribution, not abundant in tropical regions. The mature fruit is necessary for the certain determination of most of the genera and many of the species, the flowers being very much alike in all, and the leaves exhibiting great diversity in the same genus. The family is also known as Umbelliferae, a misleading designation, many other plants bearing their flowers in umbels, and several of its genera bear them otherwise.
1. Fruit ribless, scaly; flowers densely capitate (Eryngieae).
2. Fruit ribbed or rarely ribless, not scaly; flowers umbelled, the umbels sometimes compact.
A. Fruit ribless, covered with hooked prickles (Saniculae).
B. Fruit ribbed, at least its beak, the ribs rarely obsolete.
a. Fruit with both primary and secondary ribs, the latter the more prominent, armed with hooked
prickles, primary ribs bristly (Caucalieae).
Calyx-teeth obsolete; fruit dorsally flattened.
Calyx-teeth prominent; fruit laterally flattened.
b. Fruit with primary ribs only (Ammineae).
* Fruit linear or linear-oblong, several times longer than wide.
Fruit with a beak much longer than the body.
Fruit beakless, narrowed to the base.
Fruit not bristly.
Fruit beaked, the beak shorter than the body; oil-tubes none.
Fruit beakless, or short-beaked; with oil-tubes.
Annual herbs, with decompound leaves.
Perennial herb, with 3-foliolate leaves.
** Fruit oblong to ovoid or globose, not more than about twice as long as wide.
† Fruit much flattened dorsally, parallel with the commissure.
Leaf-segments toothed or incised, or leaves dissected.
Acaulescent or nearly so.
Calyx-teeth obsolete; stylopodium none.
Calyx-teeth distinct; stylopodium flat, evident.
Leafy-stemmed; stylopodium conic or depressed.
Flowers yellow or greenish-yellow; stylopodium depressed.
Fruit with thickened corky margins, the ribs obscure; perennial, native.
Fruit thin-margined, the ribs distinct; introduced plants.
Annual; leaves finely dissected.
Biennial or perennial; leaves pinnately compound with broad leaflets.
Umbels not involucrate.
Umbels involucrate, the bracts deflexed.
Flowers white or greenish-white; stylopodium mostly conic; involucre none, or of a
few small bracts, or deciduous; perennials.
Oil-tubes large, not extending to the base of the fruit.
Oil-tubes slender, extending to the base of the fruit or very nearly to the base.
Lateral wings of the fruit distinct, forming a double border.
Leaves 2-3-pinnately decompound, with narrow segments; stylopodium
Leaves ternately or pinnately compound, with broad segments; stylopodium
Lateral wings of the fruit contiguous.
Native marsh herbs; leaves pinnate, or reduced to hollow phyllodes.
Introduced field herb; leaves ternate.
†† Fruit not flattened, or flattened laterally (at right angles to the commissure).
‡ Petals yellow or greenish-yellow (sometimes deep purple in Thaspium).
Leaves entire, perfoliate in our species; fruit without oil-tubes.
Leaves compound; fruit with oil-tubes.
Fruit not flattened, all its ribs winged; stylopodium none.
Fruit laterally flattened, its ribs rot winged.
Leaf-segments entire; stylopodium none; oil-tubes many.
Leaf-segments crenate, lobed or incised.
Stylopodium present, conic or depressed.
Key to Genera.
Involucre of 2-4 linear bracts; stylopodium depressed.
Stylopodium large, conic; tall introduced plant with filiform leaf-segments.
Stylopodium depressed; low native perennials with decompound leaves.
‡‡ Petals white, greenish-white or rarely pinkish.
§ Fruit nearly terete, not flattened either laterally or dorsally, or very slightly flattened.
Umbels compound; leaves compound or simple.
Ribs of the carpels all winged.
Involucre of broad membranous bracts.
Ribs of the carpels distinct but not winged.
Ribs all corky-thickened.
Annual; leaves finely dissected.
Perennial; leaf-segments broad.
Dorsal ribs slender, the lateral sometimes corky.
Lateral ribs corky-thickened; leaves simple or simply pinnate.
None of the ribs corky-thickened; leaves compound.
Annual; leaves dissected into filiform segments; fruit subglobose.
Perennial; leaf-segments broad; fruit oblong.
Umbels simple; leaves reduced to hollow jointed phyllodes.
§§ Fruit laterally flattened.
Umbels and leaves simple; no oil-tubes in the fruit.
Ribs of the fruit not anastomosing.
Ribs of the fruit anastomosing.
Fruit tubercled or bristly.
Seed face flat.
Fruit smooth, neither tubercled nor bristly.
Carpels strongly flattened laterally; fruit nearly orbicular; plants acaulescent.
Carpels nearly terete, or only slightly flattened.
No oil-tubes in the fruit.
Seed-face concave; involucre present.
Seed-face flat; involucre none.
Fruit with oil-tubes.
Seed-face concave; oil-tubes numerous; roots tuberous.
Oil-tubes numerous; ribs filiform or inconspicuous.
Oil-tubes 1-3 in the intervals; fruit distinctly ribbed.
Umbels terminal or axillary.
Stylopodium depressed; leaves once pinnate; oil-tubes 1 - 3 in
Stylopodium conic; oil-tubes solitary in the intervals.
Ribs, at least the lateral ones, corky-thickened.
Annuals; leaves finely dissected.
Perennials; leaves decompound.
Ribs not corky-thickened.
Leaves reduced to hollow jointed phyllodes.
Umbels, at least the lower, opposite the leaves.
1. ERỲNGIUM [Tourn.] L. Sp. Pl. 232. 1753.
Mostly perennial herbs, with spiny-toothed lobed dentate or sometimes dissected, rarely entire leaves, and dense bracted heads or spikes of small white or blue sessile flowers, subtended by bractlets. Calyx-teeth rigid, pungent, or acute. Petals erect, the apex emarginate with a long inflexed tip. Disk expanded. Styles slender. Fruit obovoid or ovoid, scaly or tuberculate, ribless, somewhat flattened laterally. Carpels nearly terete, the oil-tubes usually 5. [Greek, a kind of thistle.]
About 175 species, of wide geographic distribution in tropical and temperate regions. Besides the following, about 25 others occur in the southern and western parts of North America. Type species: Eryngium maritimum L.
Plants erect, tall; stem-leaves spiny or bristly-margined.
Leaves elongated-linear, parallel-veined.
Leaves elongated-linear, reticulate-veined.
Stem-leaves palmately incised-pinnatifid.
Plants prostrate, slender; leaves unarmed.