Division of Paeonia sect. paeonia((Hong, De-Yuan. “Peonies of the World. Taxonomy and phytogeography.” Kew: Royal Botanic Gardens, 2010, pp. 55-58.))
The subdivision of Paeonia sect. Paeonia has been controversial. The first subdivision was made by Salm-Dyck (1834), who recognised seven sections in this group using characters such as the number of ﬂowers per stem, the leafflets partite or not, the shape of leaf blades, and leaf indumentum. Baker (1884) informally divided all herbaceous peonies into three sections according to indumentum (glabrous or tomentose) and status of follicles (erect or spreading when mature). Stern (1946) recognised two subsections in sect. Paeonia, subsect. Foliolatae and subsect. Dissectifoliae, which were based on the number of leaflets or segments of lower leaves. Kemularia- Nathadze (1961) grouped sect. Paeonia into three sections on the basis of petal colour, division of leaves (biternate or triternate): sect. Flavonia (including a woody series, ser. Luteae), sect. Paeon (including a woody series, ser. Delavayanae), and sect. Sternia. Uspenskaya (1987) divided sect. Paeonia into three sections, lumping Kemularia-Nathadze’s sect. Flavonia and sect. Paeon into a single section, Palaearcticae. She accepted Salm-Dyck’s Albiflorae as a section, emphasising the character of the leaf margin of P. lactiflora. Halda (2004) recognised two subgenera, four sections and four subsections in this section as follows:
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As described in Chapter 3, morphological polymorphism can account for a range of petal colours within a single population and for the glabrous or hairy characters of the carpels and follicles. Thus, Salm-Dyck’s (1834) and Kemularia-Nathadze’s (1961) subdivisions of sect. Paeonia are artiﬁcial. Uspenskaya’s (1987) subdivision is more rational, though her decision to separate P. anomala and its allies from P. lactiflora is not justified. Halda’s (2004) classiﬁcation separates a number of closely related taxa into different sections or even subgenera. Some examples: Paeonia mlokosewitschii (= P. daurica subsp. mlokosewitschii) is in sect. Flavonia, whereas P. lagodechiana is in sect. Paeonia (they were actually two colour forms in the same population from Lagodekhi, Georgia); P. parnassica is so closely related to P. arietina that it may even be treated as a subspecies of species P. arietina, but Halda places P, parnassica in subsect. Paeonia and P. arietina in subsect. Masculae; P. lactiflora, P. anomala (including subsp. Veitchii), P. emodi and P. sterniana are closely related, sharing a number of characters, but Halda (2004) separates them into two subgenera, subg. Albiflora and subg. Paeonia, the latter with two sections, sect. Paeonia and sect. Emodi.
On the other hand, Halda’s system pulls distant entities together in a single subsection. For example, P. anomala and P. hybrida sensu Halda (= P. intermedia) are both in subsect. Anomala; P. clusii (including P. rhodia), P. parnassica, P. peregrina and P. officinalis are pulled together into subsect. Paeonia.
Stern’s (1946) subdivision of sect. Paeonia into two subsections according to division of leaves is too simple, failing to recognize important characters such as number of flowers per stem, shape of sepals and form of roots.
Molecular analysis based on ITS (nrDNA) and matK (coding region of cpDNA) (Sang et al., 1995, 1997) implies that there are three groups in the section. On the basis of both morphology and DNA sequences, therefore, we here divide the section Paeonia into three subsections: subsect. Paeonia, subsect. Albiflorae and subsect. Foliolatae.
Paeonia subsect. Albiflorae
Roots more or less carrot—shaped. Leaves glabrous or with bristles along veins on the upper surface. Flowers usually several per stem, rarely solitary, or solitary but with undeveloped (sterile) ﬂower buds at axils; sepals mostly caudate at the apex. Almost all diploid with 2n = 10 (P. emodi with a tetraploid population, 2n = 20, in Xizang (Tibet)).
Included species (4): Paeonia anomala L., P. emodi Wall. ex Royle, P. lactiflora Pall., P. sterniana H. R. Fletcher.
All species in Paeonia subsect. Albiflorae are found in Asia, with the range of P. anomala extending into northeastern Europe.
Paeonia subsect. Foliolatae
Roots carrot-shaped. Lower leaves biternate; leaflets/leaf segments usually numbering 9 or more but fewer than 21 (up to 32 in P. broteri and 95 in P. clusii); leaves always glabrous above. Flowers always solitary and terminal; sepals mostly rounded at the apex. Both diploid and tetraploid with 2n = 10 and 2n = 20.
Included species (11): Paeonia algeriensis, P. broteri, P. cambessedesii, P. clusii, P. coriacea, P. corsica, P. daurica, P. kesrouanensis, P. mairei, P. mascula and P. obovata.
Disjunct; in E Asia (Japan, Korea peninsula, the Russian Far East and China) and in Europe, NW Africa and W Asia (from the western Mediterranean to Iran)
Paeonia subsect. Paeonia
Lateral roots fusiform or tuberous. Lower leaves biternate or triternate; leaﬂets nearly always segmented with leaflets/leaf segments (9—)21—340 in number; leaves mostly with bristles along veins above. Flowers solitary and terminal; sepals mostly rounded at the apex. Mostly tetraploid (diploid only in P. intermedia and P. tenuifolia).
Included species (7): Paeonia arietina, P. intermedia, P. officinalis, P. parnassica, P. peregrina, P. saueri and P. tenuifolia.
From Central Asia to the northern Mediterranean.