Flora of North America species comparison

Genera ca. 450, species ca. 3800 (76 genera, 403 species in the flora).

Apiaceae currently are divided into four subfamilies (G. M. Plunkett et al. 2004; C. I. Calviño et al. 2008b; S. R. Downie et al. 2010). Subfamily Mackinlayoideae G. M. Plunkett & Lowry are sister to the rest of the family and are characterized by having fruits that are laterally compressed with fiberlike sclereids in the endocarp, no oil ducts in the intervals between the ribs, and minute or rudimentary oil ducts in the ribs. Members of this subfamily are primarily southern hemisphere in distribution; only Centella within this subfamily is found in the flora area. Subfamily Azorelloideae G. M. Plunkett & Lowry are sister to the remaining Apiaceae, and like Mackinlayoideae, their fruits have fiberlike sclereids in the endocarp and no oil ducts in the intervals between the ribs, but the fruits are dorsiventrally compressed or not compressed and almost always have well-developed oil ducts in the ribs. Also like Mackinlayoideae, Azorelloideae are found primarily in the southern hemisphere; Bowlesia is the only genus within the subfamily found in the flora area. The remaining two subfamilies, Apioideae Seemann and Saniculoideae Burnett, share the synapomorphies of fruits without fiberlike sclereids in the endocarp but with lignified parenchymatous cells in the mesocarp (Calviño et al.). The two differ in that members of Saniculoideae have simple umbels or heads and fruits without oil ducts between the ribs but with well-developed rib oil ducts, and usually without a free carpophore, whereas members of Apioideae usually have compound umbels and fruits with well-developed oil ducts between the ribs and usually no rib oil ducts, and usually with a free, 2-fid carpophore. Saniculoideae are represented in the flora area by the native genera Eryngium and Sanicula and the introduced Astrantia. Apioideae are by far the largest subfamily worldwide and contain the remaining genera in the flora area.

Within Apioideae, the traditional classification based on morphology, especially of the fruits, has been shown by DNA-based phylogenetic studies to be highly unnatural, with most tribes and even many genera polyphyletic (for example, see S. R. Downie et al. 2010). Unfortunately, most of the well-supported clades cannot yet be differentiated morphologically, and therefore no complete phylogenetic classification has been developed. Generic boundaries within this subfamily likely will be revised significantly. These problems are especially true of the so-called perennial, endemic North American (or PENA) clade, which comprises Aletes, Cymopterus, Eurytaenia, Harbouria, Lomatium, Musineon, Neoparrya, Oreonana, Oreoxis, Podistera, Polytaenia, Pseudocymopterus, Shoshonea, Taenidia, Tauschia, Thaspium, Vesper, and Zizia (E. E. George et al. 2014). As currently circumscribed, many of these genera are difficult to diagnose morphologically and therefore challenging to identify using keys; it may be worthwhile trying to key a specimen in more than one genus.

Hydrocotyle, traditionally assigned to Apiaceae or to its own family (Hydrocotylaceae), instead belongs to Araliaceae. See the discussion under that family for more information.

Apiaceae are rich in economically important plants. Well-known food plants include carrots (Daucus carota) and parsnips (Pastinaca sativa), both grown for their roots. Celery (Apium graveolens), fennel (Foeniculum vulgare), and lovage (Levisticum officinale) are eaten for their greens. Many species are used as herbs, spices, or flavorings, including angelica (Angelica archangelica), anise (Pimpinella anisum Linnaeus), asafoetida (Ferula foetida Regel), caraway (Carum carvi), celery, chervil (Anthriscus cerefolium), cicely (Myrrhis odorata), cilantro and coriander (both Coriandrum sativum), culantro (Eryngium foetidum Linnaeus), cumin (Cuminum cyminum Linnaeus), dill (Anethum graveolens), fennel, and parsley (Petroselinum crispum). Many of these species are also used in traditional medicine, as is Centella asiatica. Several genera native to the flora area contain species used for food or medicine by Indigenous Peoples, especially Cymopterus, Ligusticum, and Lomatium; details can be found in the discussions of the relevant species. Some species are grown as ornamentals, especially members of Aegopodium, Angelica, Astrantia, Eryngium, Heracleum, Ligusticum, and Selinum.

Despite so many species being edible, some Apiaceae are notoriously toxic. Some species are poisonous when consumed, notably species of Cicuta and Conium, and possibly Aethusa; Conium maculatum, poison hemlock, is reputed to have been used to execute Socrates. Species of Ammi, Heracleum (especially H. mantegazzianum), and Pastinaca contain furanocoumarins and cause photodermatitis if the herbage is handled and then affected skin is exposed to sunlight.

The Apiaceae have some distinctive morphological features that are described using some terms often unique to the family. Some Apiaceae, especially many species of Cymopterus, Lomatium, and Vesper, produce a pseudoscape, which is a leafless section of stem between the top of the caudex and the level where the leaves diverge (usually at the soil surface but sometimes above ground). The pseudoscape is an annual structure, whereas the caudex is perennial.

Compound umbels in Apiaceae are described as follows. The first order umbel is called the umbel; the bracts subtending it, if any, are called involucral bracts. The second order umbels are called umbellets, their peduncles are called rays, and any bracts subtending the umbellets are called involucel bractlets. In Eryngium, which has heads instead of umbels, involucral bracts subtend the head, and each flower is subtended by a floral bractlet.

Specialized terms are also used to describe some aspects of floral and fruit morphology. The bases of the styles are often swollen; together these swollen bases form the stylopodium. The adaxial surface of the mericarp, where it joins the other mericarp, is the commissure. The schizocarps (and therefore the mericarps) are often compressed, either dorsiventrally (parallel to the commissure) or laterally (perpendicular to the commissure). When the schizocarps are not strongly compressed, their solid shape is described; when they are strongly compressed either dorsiventrally or laterally, their plane shape in the plane of compression (that is, the wider side) is described. Each mericarp usually has five primary ribs: one lateral rib on each edge of the commissure and three abaxial ribs on the side opposite the commissure. Sometimes secondary ribs are found between some or all of the primary ribs. Some or all of the ribs may be corky or winged. Oil ducts, which are most easily seen in a mericarp cross section, are usually found in the intervals between the primary ribs and on the commissure; sometimes, they are also found in the ribs. Those in the intervals and on the commissure are often called vittae in other literature. When the mericarps split from each other, they are suspended from a slender, rigid structure called the carpophore, which may be entire or, more frequently, 2-fid.

The petal apices in most Apiaceae bear a narrow, inflexed portion referred to here as an appendage; the apex itself may be broadly acute to deeply emarginate, and the appendage may be distinct or distally adnate to the petal’s adaxial surface. In a few genera, the petal apices are spreading and obtuse, without the appendage. Petal apices in Eryngium are inflexed but usually are lobed to fimbriate.

Compound leaves are described with the pattern of division (ternate, pinnate, or palmate) given progressively to about three orders, as appropriate. For example, “ternate-pinnate” means that the first order arrangement is ternate with each primary leaflet then being pinnate; if the primary leaflets were instead sometimes pinnate and sometimes 2-pinnate, these leaves would be described as “ternate-1–2-pinnate.” When the pattern of division is constant among numerous orders, the leaves are described as decompound.

Eight genera not fully treated here have been reported from the flora area, but none of their species appears to be naturalized.

Bifora Hoffmann resembles Coriandrum, from which it is best distinguished by lacking sepals (versus sepals well developed) and its schizocarps splitting into mericarps (versus not splitting). Bifora radians M. Bieberstein was reported from ballast in New Jersey, Pennsylvania, and Rhode Island and B. testiculata (Linnaeus) Sprengel from ore piles in Maryland. They differ in that B. radians has bisexual peripheral flowers with enlarged, irregular corollas, staminate central flowers with radially symmetric corollas, and smooth to slightly wrinkled mericarps, whereas B. testiculata has all the flowers bisexual with essentially radially symmetric corollas and strongly wrinkled mericarps.

Caucalis platycarpos Linnaeus was reported from ballast in Pennsylvania. This species would key here to Yabea but differs in having the leaves 1-pinnate with undivided leaflets 10–80 × 5–20 mm (versus 1–2-pinnate with pinnatifid leaflets, the ultimate segments 2–8 × 0.2–2 mm) and mericarps 10–12 mm (versus 3–7 mm).

Cuminum cyminum Linnaeus has been reported from waste areas in Massachusetts and Texas. This species would key here to the group of genera with bristly or hispid mericarps (first lead 8); it resembles Daucus and Yabea in having mericarps with five filiform primary ribs and four prominent secondary ribs but differs from both in that schizocarps are fusiform (rather than oblong or ovoid), and the mericarp secondary ribs are not winged and bear straight bristles that are not barbed.

Helosciadium W. D. J. Koch most resembles Apium, differing in having umbels with involucel bractlets and often involucral bracts (versus bracts and bractlets absent) and entire (versus 2-fid) carpophores. Helosciadium nodiflorum (Linnaeus) W. D. J. Koch [Apium nodiflorum (Linnaeus) Lagasca], which has stems rooting only at the base, umbels with 0–2 involucral bracts, and peduncles shorter than the rays, has been reported from ballast in New Jersey, Pennsylvania, and South Carolina and in streams in the San Francisco Bay area, California. Helosciadium repens (Jacquin) W. D. J. Koch [Apium repens (Jacquin) Lagasca] has prostrate stems rooting at most nodes, umbels with 2–3 involucral bracts, and peduncles longer than rays; it has been reported on ballast from Pennsylvania.

Selinum carvifolia (Linnaeus) Linnaeus, which was reported from a vacant lot in Boston, Massachusetts, resembles some Angelica species with mericarps bearing well-developed abaxial wings, but it can be recognized by its solid (versus hollow) stems that are strongly winged (versus not winged), at least on the distal internodes.

Seseli libanotis (Linnaeus) W. D. J. Koch was reported as a waif from the District of Columbia and Maryland. It would key here to Perideridia, differing most prominently in its caudex covered with the fibrous leaf remains (versus not with fibrous leaf remains) and its mericarps with prominent ribs and papillate and densely pubescent surfaces (versus usually filiform ribs and smooth, glabrous surfaces). It resembles Ligusticum in its fibrous caudices but differs in its well-developed (versus minute or absent) sepals, and papillate, densely pubescent (versus smooth and glabrous) mericarps. In addition, S. libanotis usually has strongly ridged stems, in contrast to the smooth stems of the North American species of both Ligusticum and Perideridia.

Trachyspermum ammi (Linnaeus) Sprague resembles Ammi majus but differs in having its mericarps more prominently ribbed and covered with minute papillae (versus smooth). It is known from a single, old report from disturbed ground in Michigan.

Turgenia latifolia (Linnaeus) Hoffmann was reported from ballast in Pennsylvania and Washington and the margin of a farm field in Oregon. It most resembles Daucus and Yabea (first lead of couplet 8), differing from both in its combination of 1-pinnate leaves with broad leaflets (versus highly divided leaves with narrow ultimate segments) and laterally compressed schizocarps and mericarps with essentially equal primary and secondary ribs all bearing barbed bristles.

In the key to genera of Apiaceae, characters and character states are sometimes used that are included in descriptions of taxa within the relevant genera but not in the generic descriptions themselves. Such characters are not usually found as part of a normal genus description (for example, measurements), but they are included in the key because they are useful for identifying some genera within the family.

(Discussion copyrighted by Flora of North America; reprinted with permission.)