Flora of North America species comparison

Genera ca. 60, species 1700 (22 genera, 284 species in the flora).

The flowers of many species of Ranunculaceae begin to open long before anthesis, while the floral organs are just partly expanded. Only mature flowers with open anthers should be used for determination of diagnostic characteristics (especially measurements).

The literature is inconsistent about the term for the whorl of organs between sepals and stamens; these may be conspicuous and petaloid, or reduced to stalked nectaries, or intermediate between the two states. They have been called petals, honey-leaves, or (when they are inconspicuous) staminodes or nectaries. We follow M. Tamura (1993) and treat as petals all organs between the sepals and stamens, except in Clematis and Aquilegia where they usually bear rudimentary anthers and clearly represent staminodes.

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

Species ca. 150 (25 in the flora).

The taxonomy of Anemone continues to be problematic. Anemone occidentalis and A. patens var. multifida (the first two taxa in this treatment) are frequently placed in the genus Pulsatilla Miller on the basis of the long plumose achene beaks, and A. acutiloba and A. americana (the last two taxa in this treatment) in the genus Hepatica Miller, primarily on the basis of the involucre immediately subtending the flower and the lobed, persistent leaves. Recent phylogenetic analyses of Anemone in the broad sense, however, indicate that both Pulsatilla and Hepatica should be subsumed within Anemone. While traditional morphologic characters are useful in distinguishing between Pulsatilla and Hepatica species, respectively, many other morphologic and molecular attributes are shared with Anemone, strongly suggesting that these genera should be united (S. B. Hoot et al. 1994). In addition, a number of genera that have been recognized primarily on a cytotaxonomic basis (e.g., Anemonastrum, Anemonidium, Anemonoides, and Jurtsevia) are reduced to synonymy here. Some North American species of Anemone are closely related to plants in Europe, Asia, and South America and continue to be recognized at different ranks. For example, Anemone patens Linnaeus var. multifida (a species included in this treatment) was called Pulsatilla multifida (Pritzel) Juzepczuk for the former Soviet Union by S. V. Juzepczuk (1970) and Pulsatilla patens (Linnaeus) Miller var. multifida (Pritzel) Li S.H. & Huang Y. H. for China by Wang W.-T. (1980). Moreover, interspecific hybridization among some sympatric or nearly sympatric North American species also contributes to the confusion (see N. L. Britton 1891; C. L. Hitchcock et al. 1955-1969, vol. 2; R. S. Mitchell and J. K. Dean 1982). Additional analyses (e.g., G. Boraiah and M. Heimburger 1964; M. Heimburger 1959; C. Joseph and M. Heimburger 1966; and C. S. Keener et al. 1995) may prove to be helpful in resolving the taxonomy within this morphologically diverse genus.

Anemone nemorosa Linnaeus, A. ranunculoides Linnaeus, and A. blanda Schott & Kotschy, all native to Europe, are cultivated and may persist in the flora. Although apparently they rarely become naturalized, A. nemorosa is established at two sites in Newfoundland and Quebec, and A. ranunculoides in Quebec. Both are close relatives of A. quinquefolia and its allies.

Anemone ranunculoides is the only species in North America combining yellow sepals with rhizomes and 1-2-ternate leaves. Anemone blanda will key to A. caroliniana or A. berlandieri in this treatment. It can be distinguished by its short-pilose achenes, in contrast to the densely woolly achenes of A. caroliniana and A. berlandieri. Anemone nemorosa will key to A. quinquefolia; it differs in having 6-8 sepals and brown or black (never white) rhizomes with a 3-5 mm diameter in contrast to the 5 sepals and white or black rhizomes with 1-3 mmdiameter of A. quinquefolia.

Protoanemonin, an irritating acrid oil, is an enzymatic breakdown product of the glycoside ranunculin and is found in many species of Anemone. While protoanemonin can cause severe topical and gastrointestinal irritation, it is unstable and changes into harmless anemonin when plants are dried (N. J. Turner and A. F. Szczawinski 1991).

A caudex, as the term is used here, is the "woody," perennating base of an aerial shoot (inflorescences and basal leaves). The word tuber refers to a swollen, more or less vertical underground stem. The aerial shoots arise from the apex of either of those persistent structures. Rhizome, as the term is used here, refers to an underground, usually horizontal stem (more or less vertical in Anemone piperi), that is nearly uniform in diameter (about 1-4 mm diam., depending on the species) along its length. Aerial shoots arise directly from nodes at or near the apex of the rhizome.

Many species of Anemone have only one type of underground stem. Some species, however, have both rhizomes and caudices. In such cases the aerial shoots arise from the apex of a caudex attached to the rhizome. Some other species sometimes have both tubers and rhizomes. In those, one or more horizontal rhizomes arise near the apex of the tuber; the aerial shoots arise from the apex of the tuber.

Proportions given in the key for the middle lobes of basal leaves are calculated as follows: measure length of lobe from apex to a line connecting bases of sinuses; and measure total length of blade from leaf apex to summit of petiole.

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