University of California Publications in Botany vol. 19, No.7 pp. 245-266 13 fig. in text (1939)


The Genus Paeonia, although small in number of species, is very complex taxonomically. Many species are extremely variable under natural conditions, and this variability is greatly increased in the horticultural forms, which are discussed by most students of the genus. In view of the great horticultural interest of most of the species, the writer feels that any information which will help' to clarify their relationships to each other and to the cultivated forms is of value. The activity of Dr. A. P. Saunders, of Clinton, N. Y., in gathering together most of the known species of the genus, in forms as near to the original wild ones as possible, and in making all possible hybridizations between them, has provided much information of this sort. During the past five years the writer has had the privilege of studying the plants of this living collection and therefore of comparing directly live plants of the various species, hybrids, and horticultural forms. Such comparison is of fundamental importance in the study of Paeonia, since the most important specific distinctions in floral characters are difficult or impossible to recognize in herbarium specimens. Also, a morphological and cytological study of Dr. Saunders' extensive series of hybrids has proved of great value in clarifying interspecific relationships. Hence the writer feels that the systematic knowledge gained through the study of the species and hybrids of the Saunders collection will help toward the final understanding of this most interesting genus.


The origin of the plants of the species in the Saunders collection is discussed elsewhere (Saunders and Stebbins, 1938). Both a knowledge of their source and a comparison with herbarium specimens confirms the opinion that, with four exceptions, Paeonia suffruticosa, P. albiflora, P. officinalis and its relatives, and P. corallina, they are morphologically and genetically identical with or closely similar to the wild species which they represent. Besides studying the living plants, the writer has examined specimens of critical species in the United States National Herbarium (cited as US), the Gray Herbarium (G), the herbarium of the New York Botanical Garden (NY), borrowed through the generosity of their curators, to whom he wishes to express his gratitude, the herbarium of the University of California (UC), and the excellent private herbarium of Mediterranean plants of Dr. Hermann Knoche, at San Jose, California (Kn), through the kind permission of its owner.

In all the herbarium specimens studied, the critical floral characteristics have proved difficult or impossible to see. Most sheets bear only one flower, so that dissection is impossible without destruction of the specimen. Moreover, if the flower is mounted so as to show the sepal characteristics, those of the disk and follicles are obscured, and vice versa. In making specimens of the plants in the Saunders collection, the only satisfactory method was to dissect one of the flowers while it was fresh, and to press the parts separately. The sepals and petals were removed and flattened out, the group of follicles was split with a scalpel or knife, and a sufficient number of the stamens removed to expose at least part of the disk. When dry, the dissected floral parts may be placed in an envelope or pocket, or they may be mounted on a separate herbarium sheet, the parts being placed in order. Although time-consuming, this method is the only one that gives adequate information on the specimen collected, and the writer suggests that future collectors who may be interested in the genus should follow whenever possible this or some similar method.

Since in some of the species complexes, particularly that centering about P. corallina, a knowledge of the chromosome number is essential for an understanding of their systematic relationships, a method of inferring this in herbarium material has been of some value. This was measurement of the length of the guard cells of the stomata, a method used also by Matsuura (1935) with Fritillaria, Sax and Sax (1937) with several genera, and E. B. Babcock and Stebbins (1938) with Crepis. Since the length of the guard cells varies with the position of the leaf on the stem, being shorter in the higher leaves, care was taken to obtain the samples for measurement from corresponding parts of corresponding leaves. In this study the side of the terminal segment of the middle cauline leaf was the part selected. Although individual variation in size was found, the average size for the known diploids was always significantly lower tlian that for the tetraploids, the former ranging from 41 to 45 ì, and the latter from 47 to 52 ì. It was slightly larger in fruiting than in flowering specimens, so that when the maturity of the specimen was taken into account, an even greater contrast between the two types was found than is indicated by these figures.


Although four monographic treatments of Paeonia exist, those of Baker (1884), Anderson (1817), Lynch (1890), and Huth (1892), none has proved entirely satisfactory in the light of the present writer's observations. Emphasis has usually been placed on vegetative characteristics, or, among flower characteristics, on such criteria as pubescence of the follicles, color, and so on, none of which has proved significant in view of the hybridization work of Dr. Saunders. A review of the most important characters and their significance is therefore presented.

1. Great importance has been attached to leaf character by all four of the monographers of Paeonia,. The resulting tendency to group together species with similar leaves has tor the most part been successful in indicating natural relationships, but in some groups, particularly the laciniate leaved forms related to P. tenuifolia and P. anomala, the great similarity of their leaves has led to the confusion of plants which in their floral characteristics are quite different from each other. Since the real relationships of these forms have been cleared up in large part by the cytogenetic studies of Saunders and Stebbins, a particular treatment of them is presented below. They are evidence that here, as in all other plant genera, leaf characteristics can be very misleading, and should be used with reservation.

2. The character of the sepals has proved the most valuable taxonomic character in the genus. Although overlooked by all the monographers, probably because of the difficulty of observing it in herbarium specimens, in which the sepals are usually hidden by the petals, this character was emphasized and well illustrated long ago for three Russian species by Pallas (1784). In the more primitive species of the genus, the sepals are indeterminate in number, and they all consist of two distinct portions, thus showing their homology to leaves. As has been described by Domin (1911) and Glück (1919, pp. 433-434), the proximal portion, corresponding either to the stipular sheath or to the petiole of a foliage leaf, more or less broadened and flattened, constitutes the sepal proper, while the distal part, corresponding to the blade, is a more or less leaflike terminal or subterminal appendage (figs. 2, A-5, a). The increasing development of the proximal and reduction of the distal portion is in these species quite gradual, and even the innermost sepal possesses the vestige of a "blade" in the form of a small mucro at or near its apex. In the more advanced species, on the other hand, the number of sepals is smaller, the transition is more abrupt, and at least the innermost sepal lacks even the rudiment of a "blade" (figs.10 ,A-13 ,A). In the most extreme species, P. obovata (fig. 13, a), the sepals are definitely three in number and are all nearly alike, none possessing a rudimentary "blade."

3. The staminodial disk lias been used by Huth (1892) and others to separate the three subgenera, and is undoubtedly of value. the close resemblance, however, between the disks of P. Delavayi and P. albiflora (figs. 2, b; 3, b), which belong to different subgenera, reduces its significance somewhat. Within each subgenus there are differences in the disk which hold with some constancy, although they arc of greater value in delimiting subspecies and varieties than in separating the main species complexes.

4. The position of the mature follicles—whether erect, spreading, or re-flexed—is, as has been indicated by the monographers, of some importance. There is difficulty in using this cliaracter, however, because fully mature, completely ferthe follicles, which alone can be used as a basis tor comparison, are not encountered frequently enough in herbarium specimens.

5. The pubescence of the follicles has been given great weight by the monographers. This character is of use in delimiting many of the subspecies or varieties, but, unaccompanied by other differences, is as unreliable as characters of pubescence are in most other plant genera. For instance, although typical P. albiflora is stated by all the monographers to possess glabrous follicles, and does for the most part, yet one natural variety (var. trichocarpa Bunge), and several horticultural forms including the well-known var. Whitleyi major, have the follicles tomentose. A similar difference is present among wild varieties of P. anomala.

6. The shape of the summit of the ovary and the stigma has been used by Finet and Gagnepain (1904) in their excellent treatment of the eastern Asiatic species, and has proved of value in the separation of species complexes as well as subspecies or varieties.

7. The size, shape, and surface markings of the seeds, as indicated in the key presented below, and illustrated in figure 1, are among the fundamental characters separating the three subgenera. Also of value is the peculiar wrinkling of the seed coat in many of the species having entire leaflets.


A full account of the cytology of the species is presented elsewhere (Stebbins, 1938a). First, the basic chromosome number throughout the genus is five pairs; second, the species differ very little in the size and morphology of the chromosomes (Stebbina, 1938a); and third, there are a number of tetraploid species. These tetraploids, with 20 rather than 10 as their somatic chromosome number, are either closely similar morphologically to the diploids, such as the tetraploid forms of P. corallina, P. Corsica, and the putative tetraploid of P. Broteri, or they show combinations of the characteristics of different diploids, as in P. officinalis and its relatives, P. coriacea, P. Wittmanniana, and P. Willmottiae. Only one tetraploid, P. tomentosa, diverges morphologically from any of the known diploids. These tetraploids account for much of the systematic difficulty in the genus. All of them intercross with ease, and many give ferthe or partly ferthe progeny (Saunders and Stebbins, 1938). Furthermore, some of them are undoubtedly allopolyploids; that is, they are derived from hybrids between two diploid species by doubling of the chromosome numbers. These allopolyploids often include varieties which form an almost complete transitional series from one of their original diploid ancestors to the other. The origin of such series is presumably through segregation, caused by quadrivalent formation in the allopolyploids, and through the occasional production of ferthe offspring from backcrosses. The exact methods are, however, not clear. Nevertheless, some of the diploid species which originally were probably quite distinct from each other have been linked together by a series of intermediate allopolyploid derivatives. These series are particularly well developed in the species with entire leaflets. The three diploid species, P. triternata, P. broteri, and P. Cambessedesii, are distinct from one another, yet are apparently linked together by a series of allopolyploid derivatives, one of which is the true P. corallina. This group is a typical example of a polyploid complex as defined by Babcock and Stebbins (1938, pp. 55—57). A further discussion of this complex is given below.

In the key to the species of the subgenus Paeon here presented, the key letter setting off each tetraploid is marked with an asterisk. In these tetraploids variability and overlapping with the nearest diploids usually occurs.


The following key gives what are, to the writer, the most salient characteristics of the three subgenera.

Key to the subgenera of Paeonia

A. Disk conspicuous, one-third the length of the follicles, or more, scalloped or lobed; seeds large (10-15 mm. long), their surface dull, under a lens coarsely rugose with irregular longitudinal ridges. (Fig. I, A)

B. Plants herbaceous; petals shorter than to slightly longer than the sepals; disk wholly or partly divided into fluted or ridged lobes.................... Subgenus Onaepia

B. Plants woody at the base; petals definitely longer than the sepals; disk continuous, somewhat scalloped at the apex. (Fig. 2, B) ..................... Subgenus Moutan

A. Plants herbaceous; petals definitely exceeding the sepals; disk relatively inconspicuous or absent, less than one-third the length of the follicles at anthesis (except in occasional lateral flowers of P. emodi), forming a continuous, undulate ridge, or somewhat scalloped; seeds smaller (5-11 mm. long), their surface more or less lustrous, under a lens minutely rugose through the elevated polygonal areas of the surface cells. (Fig. 1, B-F) ......................... Subgenus Paeon

Subgenus Onaepia Lynch, Jour. Roy. Hort. Soc., 12:433, 1890. Sect. II. Nearcticae, Huth, Engl. Jahrb., 14:273, 1892.

This, the American subgenus of Paeonia, has been treated elsewhere (Stebbins, 19386).

Subgenus Montan Lynch, ibid., 432. Sect. I. Palearcticae, Fruticosae, Huth, 1. c., 272.

The shrubby habit of the species of this subgenus, as well as their restriction in range, suggest primitiveness and great age. The shrubby habit is not necessarily a sign of primitiveness in plants, but it is certainly so in Paeonia, as has been demonstrated in the anatomical study of Kumazawa (1935). Furthermore, the species of this subgenus occur naturally only in the mountains of western China, a region noted for its wealth of old, "relic" species. Only two species are recognized, P. Delavayi and P. suffruticosa.

P. Delavayi Franch, Bull. Boc. Bot. Fr., 33:382, 1886.

The reduction of P. lutea Fr. to a variety of this species by Finet and Gagnepain (1904) is well supported by its behavior in the Saunders garden. It hybridizes freely, and most of the seedlings raised by Dr. Saunders from his original plants are mixtures of the two forms. Cytologically, the two pure varieties and the hybrids are all indistinguishable from one another. That hybridization also occurs naturally is evident from the intermediate flower color in some herbarium specimens; for example, between Muli and Kulu, Southwest Szechuan, Beck no. 24123 (DC).

P. Delavayi var. angustiloba Rehder and Wilson, PIantae Wilsonianae, 1, 318,1913.

This is a weak variety, and its elevation to a species, P. Potanini, by Komarov (Not. Syst. Herb. Hort. Bot. Petr. II. 7.1921) is wholly unjustified.

P. Delavayi is undoubtedly the oldest, most primitive species of the genus. It shows relationships with members of both of the other subgenera, resembling the American species of the subgenus Onaepia in the character of its seeds, and approaching them in the size and scalloping of its disk and the size and color of the petals, while it approaches P. Emodi and P. anomala of the subgenus Paeon in the character of its leaves and sepals, and resembles them in the shape of its follicles and stigmas.

P. suffruticosa Andr., Rehder (1913, 1920, 1925).

To Rehder's careful discussions of this species the present writer has nothing to add. In the peculiar triangular shape of its sepals, and particularly the extreme development and the thin, membranous texture of its disk, P. suffruticosa is definitely more specialized than P. Delavayi.

Subgenus Paeon, Lynch, I. c., 434. Sect. I. Palacarcticae; 1. Herbacae, Huth, 1. c,, 265.

This subgenus is much the largest and most widespread. The following key presents the species relationships as conceived at present by the writer, excluding those not sufficiently known to him. See also the key to hybrid forms, p.259.

Key to the species of subgenus Paeon

A. Midrib of the innermost sepals prominent and extending to the apex, where it is generally prolonged into a mucro or a linear appendage 1-15 mm. long; leaves ternate; primary divisions deeply lobed but never completely divided; stems bearing 2-5 flowers, except in forms of P. anomala.

B. Leaves not impressed veined, glabrous on both surfaces, their edges minutely scabrous-dentate under a lens; flowers erect; follicles (including the stigma) at anthesis 9-16 mm. high, erect or somewhat spreading at maturity ............... P. albiflora Pall.

B. Leaves impressed veined, scabrous-pubescent on the main veins above, and sometimes on the margins and main veins beneath, the edge not scabrous; flowers more or less nodding; follicles (with stigmas) at anthesis 6-12 mm. high, distinctly spreading and sometimes nearly horizontal at maturity.

C. Terminal division of the largest leaves 5-lobed; disk 1.5-2.5 mm. high; follicle solitary or rarely 2; seeds 9-11 mm. long ..................... .P. Emodi Wall.

C. Terminal division of the largest leaves with 12-25 lobes; disk 0.2-1.2 mm. high; follicles 2-4; seeds 6-8 mm. long ............................... P. anomola L.

A. Midrib of innermost sepal inconspicuous, not extending to the strongly rounded tip of the sepal; newer always solitary.

D. Roots fascifled; leaves once or twice ternate, the divisions cleft into a large number of lanceolate or linear lobes; sepals 6-9; stigmas erect or scythe-shaped ............ P. tenuifolia L., P. hybrida Pall., etc. (see pp. 255-259)

D. Roots not fascicled; leaves (except in forms of P. officinalis) twice ternate, or the lateral divisions pinnately parted; ultimate leaflets entire or with lanceolate to elliptic lobes.

E. Ultimate leaflets lobed; sepals 4-7, mostly 5 or 6................ P. offlcinalis L.

E. Ultimate leaflets entire; sepals mostly 3—5.

F. Sepals 3-5, the outer one or two with a foliaceous appendage, markedly different from the inner in size and shape (figs. 10, A.-12, A) ; petals obovate, the apex obtuse or rounded.

G. Follicles with an obtuse or rounded apex and a sessile stigma (figs. 10, A- 11, A) becoming reflexed at maturity.

I. Entire plant strongly suffused with a reddish anthocyanin pigment; leaves dark green, thick and coriaceous; innermost sepal 1 ½ - 2 times as long as broad; pubescence of follicles brownish, strongly persistent at maturity; mature seeds with a strongly wrinkled or reticulated seed coat .............. P. corallia, Retz vars. P. Broteri Boiss. et Reut.

I. Anthocyanin pigment less noticeable, mostly pale pink, at least some part of the stem or leaf petioles greenish or yellowish; leaves dull, mostly bluish green; innermost sepal nearly or quite as broad as long; pubescence of follicles whitish, more or less deciduous at maturity; seed coat rough under a lens, but only slightly or not at all wrinkled at maturity ............P. triternata

G, Follicles attenuate at the apex (fig. 12, b) at maturity, erect, spreading, or somewhat reflexed; seed coat reticulate or wrinkled at maturity. (Fig. 1, F)

H. Leaves conspicuously hirsute beneath; flowers white or yellow ............ P. Wittmanniana

H. Leaves glabrous or slightly pubescent beneath; flowers reddish or pinkish.

I. Leaves not glaucous; follicles 20—30 mm. long at maturity; stigma curved from near the base .....P. Corsica Sieb.

P. Cambessedesii Willk.

I. Leaves strongly glaucous, follicles 35-50 mm. long at maturity; stigma elongate, the lower part straight .......... P. coriacea Boiss.

F. Sepals 3, unappendaged, subequal (fig. 13, a) ; petals elliptic, mostly acute; disk rudimentary; follicles glabrous, attenuate at the apex ...... .P. obovata Maxim.


P. albiflora Pall.

This species, the common peony of cultivation, is well isolated genetically from all the other species. It crosses with great difficulty or not at all with the other diploid species (Saunders and Stebbins, 1938), and the hybrids between it and the tetraploid species are highly sterile triploids. There is therefore little reason to believe that any of the cultivated varieties of P. albiflora are derived through hybridization between it and other species. All these cultivated varieties so tar investigated cytologically by Langlet (1928) and the present writer (1934, 1938o) are diploid, and in their meiotic behavior they resemble closely such species as P. tenuifolia and P. Emodi, forms of which nearly or quite identical with the wild species have been studied. Furthermore, they do not diverge from wild P. albiflora in any fundamental characistics that bring them nearer to any of the other species, whereas all the hybrids produced by Dr. Saunders, using P. albiflora as one parent, are very different in many respects from any of its cultivated varieties (cf. Saunders and Stebbins, 1938). The following specimens of wild P. albiflora have been compared with specimens of the cultivated varieties.

manchuria : Jalartun, P. H. Dorsett no. 3491 (UC); near station Eho, North Manchurian Railway, A. D. Voilykoff in 1923 (UC). kobea : Without locality, K. S. Gilbert no. 71 (UC). north china: Chai Tao Tzu Kou, near Jehol, J. C. Liu no. L654 (UC); Hsiao Wu T'ai Shan, Chihii, Liv no. L1734 (UC).

P. Emodi Wall., Cat. no. 4727. P. anomala var. Emodi Huth, Engl. Jahrb., 14:269, 1892.

The reduction of this species to a variety of P. anomala is not in accord with the present study. The single follicle is a most distinctive characteristic of it, the disk is larger and more definitely toothed, and the seeds are markedly larger than those of any other species of the subgenns Paeon. Furthermore, the hybrid between it and P. anomala "Beresowskii" is sterile, although all hybrids between different forms recognized as belonging to P. anomala have so far proved fully ferthe (Saunders and Stebbins, 1938). In its disk and seed characters it approaches P. Delavayi more nearly than does any other species of Paeon, and may in these respects be considered the most primitive species of its subgenus. Within its natural range, the Himalayan region, it is the only species occurring, and it is separated by about one thousand miles from the nearest P. anomala. Considerable variation occurs in the character of the innermost sepal (figs. 4, A; 4, B).

P. anomala L., Mant., 2:247,1771.

P. anomala vars. typica and nudicarpa Huth, Engl. Bot. Jahrb., 74:269, 1892.

P. Veitchii Lynch, Gard. Chron., 46:2,1909.

P. Beresowskii Komarov, Not. Syst. Herb. Hort. Pet., 2:S, 1921.

P. Woodwardii Stern, Jour. Boy. Hort. Soe., 56:76, 1931, nomen nudum.

This species is unusually variable, and includes a number of forms recently

introduced into cultivation as distinct species. Although these differ among themselves, not only in vegetative but also in floral characteristics and in time of blooming, and breed more or less true to type, they intercross with ease, and such hybrids as have bloomed (to the date of the present writing) are completely ferthe, and cytologically indistinguishable from their parents. Although Komarov with his description of P. Beresowskii (I. c.) gives a key to the members of this complex known to him, careful study of the series of specimens of P. anomala in the American herbaria has demonstrated to the present writer that this key is unworkable. Komarov distinguishes the Siberian P. anomala from the Chinese forms by its glabrous follicles, although Huth (1892) lists several specimens from Siberia under his var. typica, which is characterized by "carpellis junioribus pilosis"; moreover, a specimen from Russian Lapland—Lapponia Ponojensis, ad pagum Ponoj, Montell no. 212 (UC)—seen by the writer has follicles as tomentose as those of P. Veitchii and P. Beresowskii (fig. 5, A). Komarov distinguishes P. Beresowskii from P. Veitchii by its pale pink petals and gradually acuminate sepals, the petals of P. Veitchii being characterized as deep rose or purple, and the sepals as round-acuminate. However, among the numerous specimens of P. anomala from China seen by the writer, the two types of sepals have been found indiscriminately, and this difference does not seem to be correlated with any others. As for the difference in flower color, the notes on one collection, Bock no. 12235, from the Choni River basin, Kansu Province, read "flowers pink, white, or dark rose red," indicating that a complete aeries of variation from the flower color of P. Veitchii to that of P. Beresowskii may be found within the same colony. Another form of this species is that grown under cultivation as Paeonia Woodwardii. This is a dwarf plant, with sepals of the same shape as those of P. Beresowskii, but with rose-colored flowers, and small petals and anthers. It blooms two weeks earlier than Beresowskii, and about a week earlier than Veitchii. The size and early blooming habit of this form indicate that it is a high-altitude form, and its origin is the extreme northwest part of China, adjacent to Tibet (cf. Stem, 1. c.). Among the herbarium specimens collected in this region by J. P. Bock are some which closely resemble this form, as well as forms transitional between it, P. Beresowskii, and P. Veitchii, similar to those which have been produced in the Saunders garden by hybridization. Since no indication has yet been found that any of these three forms (P. Veitchii, P. Beresowskii, and P. Woodwardii) has a definite geographic range, they seem best regarded at present as ecological variations of one polymorphic species, and hence without definite taxonomic rank. Since, however, they are grown under cultivation as distinct types, a key to them is here presented.

Key to cultivated forms of P. anomala

A. Innermost sepal rounded or notched at the apex; petals 3.5—5 cm. long; disk well developed, 1-1.2 mm. high.

B. Plants strictly 1-flowered; innermost sepal emucronate or with a short mucro 0.5-2 mm. long; follicles usually glabrous or at least glabrate at maturity .... P. anomala (Siberian form)

B. Plants often 2-4-flowered; innermost sepal with a definite mucro 1.5—7 mm. long; follicles definitely tomentose at maturity ................... P. anomala "Veitchii"

A. Innermost sepal more or less attenuate toward the well-developed mucro; petals 2-4 mm. long; disk relatively little developed, 0.8 mm. high or less.

C. Outermost sepal 6-7.5 mm. long; petals 3.5 - 4 mm. long, somewhat notched at the apex, cream color to pale pink; stigma cream color; plant flowering late (late May or early June in central New York) ......................P. anomala "Beresowskii"

C. Outermost sepal 3.5-5 mm. long; petals 2-2.8 mm. long, entire at the apex, deep rose color; stigmas pink; plant flowering early (early to mid-May in central New York) ...... P. anomala "Woodwardii"

The following are typical of the specimens of P. anomala seen by the writer:

russia : Lapponia Ponojeusis, in vallicula rivuli ad pagum Ponoj, Vontell no. 212 (IJC).

siberia : Iter Ircutense ad fl. Lena et Kirenga, N. I. Kusnezow no. 114 (NY); prov. Semipalatinsk distr. Buchtarminsk, ad. fl. Ak-tei in fl. Buehtarma influct, Tzumantzcv et Takovlev in 1814 (NY); Zaisank, southern Siberia, P. N. Meyer no. 754 (DC, 0).

china : Baurong to Tacliienlu by way of Hadjaha, 2750-4000 m., Szechuan Province, //. Stvvens nos. 261, 460 (NY); Sungpaii Hsien, Szechuan, Fang nos. 4723,6037 (0) .Ma-pien Hsien, 3500m., Szechuan, Wang no. 22930 (&); T'ao Kiver basin, Choni River basin, common up to 10,000 ft. (3030 m.), Kansu Province, J. F. Rock no. 12235 (NY); T'ao River basin: Valley-Kwadjaki, Choni, alt. 9500 ft. (2880 m.), Kansu, /. P. Bock no. 12276 (Q).

P. anomala is most closely related taxonomically to P. Emodi, and less closely to P. albiflora. The great difficulty with which P. albifiora crosses with any of the forms of P. anomala, and the very sterile morphologically abnormal hybrids resulting from this cross (Saunders and Stebbins, 1938), suggest that the genetic relationship between the two species is more remote than is indicated by their external appearance. In the shape of its leaves, sepals, and follicles, P. anomala somewhat resembles P. Delavayi, and along with P. Emodi it may be considered the most primitive species of the sub-genus Paeon.

P. tenuifolia L., P. hybrida Pall., and their relatives (figures 6-9, p.256)

One set of hybrids produced by Dr. Saunders explains at least in part the problem of P. hybrida. Pallas (Flora Rossica, 2:94, t. 86, 1784) originally described and illustrated as this species a plant which he found growing in the garden between plants of P. anomala and P. tenuifolia, and which was apparently derived from a seed produced by the latter. Since the plant was sterile, he at first believed it to be a hybrid between these two species. Later a plant apparently identical with it, but ferthe, was found growing wild in southeastern Russia and Siberia, and on the basis of this discovery Pallas considered P. hybrida a good species. Since then P. hybrida lias been considered by some authors a variety of P. tenuifolia, by others (Huth, 1892) a variety of P. anomala, and by still others (Krylov, 1931) a good species. P. intermedia C. A. Meyer ex Ledeb., Fl. Alt., 2:277, is probably synonymous with P. hybrida.

The original belief of Pallas about the plant discovered in the garden at Leningrad has been confirmed by the repetition of the cross P. tenuifolia x P. anomala. The F1 plant of this cross agrees exactly with the description and illustration of Pallas, and, like the plant described by him, is almost completely sterile. It is, furthermore, identical with specimens of wild P. hybrida from western Siberia and Turkestan, except that the latter have apparently completely ferthe pollen.

Several other plants must be considered in this connection. One was received by Dr. Saunders from Barr and Sons (London, Eng.) as P. tenuifolia var. hybrida. Another, received from Lemoine as P. tenuifolia var. latifolia, is identical with it. Both are ferthe tetraploids, and therefore quite different cytologically from true P. hybrida, and they differ also from both P. tenuifolia x P. anomala and the wild P. hybrida in their leaves, which are pubes. cent beneath; in their inner sepals, which are much larger; and in their follicles, which at anthesis are also much larger. the stomata of these plants are, like those of all tetraploid species of Paeonia, larger than those of the diploid species and hybrids (average length of guard cells, 49-50»t). In the specimens of wild P. hybrids cited above, the length of the guard cells (average 44-45^) is the same as that in typical P. tenuifolia, and indicates that they are diploid.

No specimens of a wild plant corresponding to the tetraploid "P. tenuifolia var. hybrida" have been seen. Of the origin of this tetraploid there are two possibilities: either it is a wild form of southern or southeastern Russia, and as such is different from the plant of Turkestan and Siberia, or else it is of unknown garden origin.

P. Smouthi Van Houtte, Hort. Universel, 4:274, 1846.

Two other forms similar to the members of this group are often erroneously named P. anomala. One, P. Smouthi, is a sterile hybrid of known garden origin between P. albiflora and P. tenuifolia, and resembles closely some of the F1 plants of the same cross produced by Saunders (cf. Hicks and Stebbins, 1934; Saunders and Stebbins, 1938; Stebbins, 1938a). It was first advertised by Barr & Sons as P. anomala intermedia, and later as P. anomala typica, and was also distributed by the Old Farm Nurseries, Booskop, Holland, as P. anomala.

P. tenuifolia x triternata.

The other form is represented in the Saunders garden by four clones, all received as P. anomala, and several seedlings of known hybrid origin. Three of these clones were received from Barr & Sons, the first originally under the name P. anomala, but later changed (in litt.) to P. anomala intermedia, the second as P. anomala insignis. The fourth clone was purchased from a German firm as P. anomala.

x Paeonia Saundersii hybr. nov. (P. tenuifolia x tritemata). Planta ca. 5 dm. alta; segmenta foliarum laeiniato-pinnatifida, supra glabris, subtus minute et sparse pubescentibus vel glabris; sepala 6-7, extimum foliacenm, integrum et linearo-lanceolatum vel pinnatifidum cum 3-5 lobis lanceolatis, intimum rotundatum, emucronatum; petala obovata; discum 1-1.7 mm. altum; follicula (cum stigmo) ad anthesin 14—19 mm. longa, erecta, dense tomentosa, ad maturitatem horizontaliter patentia, 25-30 mm. longa; stigma plus minusve recurvata.

Plant 5 dm. high; divisions of the leaves laciniate-pinnatifid, the lobes linear-lanceolate, 3-12 mm. broad, glabrous above, minutely and sparsely pubescent below or glabrous, acute or acuminate; sepals 6-7, the outermost entire and linear-lanceolate or pinnatifid with 3—5 lanceolate lobes, the innermost rotund, cup-shaped, emueronate, 6-7 nerved, 20-25 mm. long and 18-25 mm. broad; petals obovate, 3.5-5.5 mm. long, 2-5 mm. broad, red, pink, or yellowish pink; anthers 3-5 mm. long; disk 1-1.7 mm. high, somewhat undulate ; follicles (with stigma) at anthesis 14—19 mm. long, erect, densely tomen-tose, at maturity horizontally spreading, 25-30 mm. long; stigma more or less recurved.

The natural occurrence of this hybrid has been reported by Maleev (1937). In cultivation, forms apparently identical with those described by Maleev are distributed erroneously as P. anomala, and under the following names given to various clones by Barr & Sons: P. anomala "Peter Barr," and P. anomala "insignis." Later Barr & Sons (in litt.), following the advice of the late Dr. Otto Stapf, designated these forms with tomentose follicles as P. anomala intermedia.

From true P. anomala this hybrid differs conspicuously in its narrower, more numerous leaf segments; in its sepals, the innermost of which in P. anomala is much less conspicuously cup-shaped, and is either mucronate or with a conspicuous midrib; in the color of its flowers, which in P. Saundersii have the red of P. tenuifolia more or less evident, and lack the magenta sliades most characteristic of P. anomala; and in its follicles, which in P. Saundersii are larger both at anthesis and (notwithstanding their sterility) at maturity.

P. hybrida (P. intermedia) is much more like P. Saundersii, and superfi-cially they are very difficult to distinguish from each other. In P. hybridii, however, the leaves are more finely dissected than in P. Saundersii, and their pubescence is either absent or confined to the main veins, both above and below, and to the margins; in P. Saundersii pubescence is distributed evenly, though sparsely, over the undersurface. The former type of pubescence is characteristic of forms of P. anomala, the latter of P. triternata. The flowers of P. hybrida are smaller in all their parts, and the disk is absent or rudimentary, the follicles are less spreading at maturity (in both the sterile garden hybrid and the ferthe wild form), and the stigma is less strongly recurved.

This hybrid has been produced in three different ways by Dr. Saunders, and several plants of it of known origin are in existence. The first two series are reciprocal hybrids between P. tenuifolia and the yellow-flowered form of P. triternata, P. Mlokosewitschii (for a discussion of this species, see below). They are identical with the forms distributed as P. anomala, except that their flowers are not red, but salmon pink or somewhat yellowish. The third group, which has only recently come into bloom, has as its parents the same clone of P. tenuifolia as the other two, and a plant of typical P. triternata received (as P. corallina) from Correvon et Cie. This differs from the other plants mentioned in that its leaves are completely glabrous below, and its flower (as is characteristic of young plants blooming for the first time) is somewhat smaller. The foregoing description includes all the plants mentioned.

Since this hybrid has not only been found several times in the wild state (cf. Maleev, 1. c.), but is also not infrequent in cultivation, and is, in the gracefulness of its foliage and the size and color of its flowers, one of the finest of the single peonies, a name for it seems to be desirable. It is with great pleasure that I dedicate it to Dr. A. P. Saunders, who first produced it from known parents and through whose labors so much has been learned both horticulturally and scientifically about this genus.

In order to clarify the distinctions between the various species, hybrids, and horticultural forms described above, a key to them is presented:

Key to P. anomala, P. tenuifolia, and related forms:

A. Innermost sepal mucronate, or at least with a strongly developed midrib which continues to its apex (figs. 5, a; 6, a) ; follicles glabrous or ahort-pubeacent; stem often 2-4-flowered.

B. Leaves scabrous-pubescent on thy midrib and often on the veins above, impressed veined, smooth and shining beneath, the lobes of the leaflets lanceolate or elliptic; petals 2.5—4.5 cm, long; plants with ferthe pollen and always producing seed. . ..... P. anomala

B. Leaves glabrous throughout, not impressed veined, lobes of the leaflets lance-linear; petals 5-6 cm. long; plants with partly sterile pollen, rarely producing seed ........ P. Smouthi (P. albiflora x tenuifolia)

A. Innermost sepal rounded, its midrib indistinct and never extending to the apex; follicles always pubescent; flower always solitary.

C. Roots fusiform; leaves glabrous below; follicles 9-13 mm. high at anthesis; disk 0-1 mm. high.

D. Leaf lobes narrowly linear, 1-2 mm. broad, very numerous, dorsal edge of the erect stigma straight except at the slightly recurved apex; disk absent .................P. tenuifolia

D. Leaf lobes 2-5 mm. broad, less numerous; stigmas more or less recurved and scythe-shaped; disk 0.5-1 mm. high ............................... P. hybrida

C. Roots not fusiform; leaves generally pubescent below; follicles, including the stigma, 13-19 mm. high at anthesis; disk a continuous fleshy ring 1-1.7 mm. high.

E. Leaves strongly pubescent below, the pubescence in living specimens visible to the naked eye; innermost sepal 12-17 mm. broad; follicles at anthesis 13-14 mm. high; partly ferthe tetraploids with good pollen .............. P. tenuifolia "hybrida"

E. Leaves minutely short-pubescent below, the pubescence visible only under a lens, and sometimes almost invisible in dried specimens; innermost sepal 18-25 mm. broad; follicles at anthesis 14-19 mm. high; sterile hybrid ........ x P. Saundersii

Paeonia officinalis L., Sp. Pl. ed., 2:747, 1762.

The relationships of this species and its relatives are far from clear, although their behavior in the garden indicates that all the forms referred by Huth to P. peregrina as well as to P. decora are interfertile and intergrade freely, so that they all belong to the same species. A further treatment of the species will be presented in a later publication in which evidence concerning its probable origin will be presented.

P. tomentosa Stapf, Bot. Mag., 185, Tab. 9249,1931.

The writer has seen only the plants in the Saunders collection, which agree closely with the original description and illustration. In its rugose, impressed veined leaves, large, brown-tomentulose sepals, and remarkably broad, almost reniform petals it differs from any other species known to the writer, although in the absence of a disk and the shape of the follicles and stigmas it agrees with P. corallina and P. Broteri. It is the earliest to bloom of all the species in the Saunders collection, and flowers about three weeks earlier than the other tetraploid forms of the corallina series. It forms sterile hybrids with P. Wittmanniana, which is to be expected in view of the great difference between the two species in the shape of the sepals, petals, follicles, and stigmas.

Notes on P. corallina Retz., P. Russii Biv., and P. Broteri Boiss. et Reut. (Figures 10-13, p. 261)

The interrelationships of the whole group of species with entire leaflets and rounded, emucronate sepals are so complex, and liave been so much complicated by hybridization in cultivation and the description of species on insufficient characters, that an adequate treatment is impossible without an extensive study of the specimens in the various European lierbaria and the species in their native habitats. However, the cytogenetic studies have revealed some facts which may be of help to an eventual understanding of this complex. There are, besides the very distinct P. tomentosa, at least four groups of species that are represented by diploid forms which are quite distinct from each other, that apparently cross with difficulty (so far as the experimental evidence goes), and that are well isolated from each other geographically and therefore must represent distinct species. These diploids are P. Broteri, P. triternata, P. Cambessedesii, and P. obovata. There is also a large number of tetraploid forms which in their morphological characteristics and in some measure their geographic distribution bridge the gap between the diploid forms. At present the writer is not certain whether these tetraploids form a series of species morphologically distinct from the diploids or whether there is so much intergradation that they must be merged with their nearest relatives among the diploids. If it is the latter that is so—and it seems the more probable situation, so far as judgment is based on the writer's present knowledge—at least one of the tetraploids, P. corallina Retz (the older name), must be taken as the nomenclatorial type of the group which it represents. However, the names of the diploids are retained at present, since they are better characterized by their original descriptions, and their relationships with each other are better understood.

P. Broteri Boiss. et Reut., Diagn. PI. Nov. Hisp., 4.

The first group of species centers about the diploid P. Broteri, a characteristic form of southern Spain. It is characterized by a strong development of reddish anthocyanin pigment or its vegetative parts; completely glabrous leaves, the largest of which are pinnately rather than ternately compound, and have narrowly elliptic leaflets 2 ½ -3 times as long as broad; elongate sepals, the innermost 2- 2 ½ times as long as broad; the disk obsolete or nearly so and completely covered with tomentum; the follicles densely brown-tomentose, abruptly contracted at the apex to the broadly scythe-shaped stigma, and the seed coat strongly reticulate-wrinkled. The following specimens are characteristic:

Spain : Sierra de Segura, E. Bourgeau in 1850 (G, Kn); Orazalema, Andalusia, E. Keverchon (NY).

Portugal; Prope Ingote non procul Conimbria, A. Moller no.l510(G,Kn).

Within the same region there occur very similar forms which, on the basis of their stomatal size, are apparently tetraploid. These pass gradually into forms corresponding with P. Bussi Biv., in which the leaves are hairy below and are never pinnate, the leaflets are shorter and broader, and the sepals are somewhat shorter. Although no chromosome counts have been obtained, evidence from stomatal measurements indicates that both diploid and tetraploid races of the Russi type exist. The following may be cited;

Spain : Cerro de Maehotte, prope Escurial, M. Winklcr in 1876 (Kn) (2n=20t); Sierra de Oredos, Bourgeau in 1863 (Kn) (2n=201).

Portugal: Serra de Arrabila, J. Daveau in 1879 (0, Kn) (2n = 201).

Sicily: Palermo, H. Boss no. 304 (G, NY, Kn) (2n = 10 and 2n = 201); in nemoribus, Incono no, 551 (Kn) (2n=20t).

Sardinia: reg. centr. or., in Monte Uliena, C. For-syth in 1884 (0, Kn) (2n = 101).

Cyprus : In sylvis Mentis Troados, Sintenis etKigono.854 (Kn) (2n=20t).

Asia Minor: North of Beilan, Syria, ex herb. Postian apud Colleg. Syriens Protestants no. 219 (US) (2n = 10T);

Armenia Rossica, Szovitz (0,US) (2n=10t).

Finally, there is a series of plants, all of them tetraploid, which combine the characteristics of P. Broteri and P. Russi with those of P. triternata, and which also approach P. Corsica and its relatives. These fit the original description of P. corallina Retz. (Obs., 3:34,1783) as well as Huth's (1892) characterization of P. corallina var. typica. They have the reddish stems and leaf veins of P. Broteri and P. Russi, though in less marked form; the leaves are ternate, and the leaflets are pubescent along the veins below; the sepals are similar: in shape to those of P. Russi, and mostly small (innermost sepal 15-25 mm. long by 12-16 mm. broad). The disk is usually little developed and is always tomentose, and the follicles, though less strongly tomentose than in P. Broteri and P. Russi, are definitely yellowish and are abruptly contracted at the apex. The following specimens may be cited:

France : Les Montils, pres Blois, Loire-et-Cher, L. Mathonnet no. 372 (Q, Kn). Monts de Cagne, Bonifacio,

Corsica, 0. Deaplantes in 1933 (Q).

Sicily : In sylvaticis Hebrodum, Madonie, Leresche in 1844 (US); prov. Sassari, silva de Bullei, 600-700 m.

Sardinia : F tort and Tiana no. 1853 (G).

P. triternata Pall., not. Act. Petr., 10:312.

P. Mlokosewitschii Lomak, Trud. Tifl. Bot. Sad., 2:282,1897.

The next series is the group centering about the Crimea and the Caucasian region, all of them diploids. These include P. triternata Pall. and P. Mlokosewitschii Lomak, two forms which are perfectly interfertile and undoubtedly belong to the same species. They are characterized by the weakly developed anthocyanin pigment on their stems and its absence from their leaves; twice ternate leaves whose undersurface is minutely and evenly pubescent; large sepals (the innermost 2.7-3.5 cm. long and nearly as broad), which are strongly veiny; a well-developed, glabrous disk; and follicles which are densely but rather shortly white-tomentose and shaped like those of the Broteri-corallina complex. No specimens have been seen by the writer which would enable him to tell whether or not the yellow-flowered, narrow-leaved form, P. Mlokosewitschii Lomak, is a distinct geographic segregate and hence entitled to varietal or subspecific rank. The following specimens are typical of P. triternata:

Russia: Prope Jaltam, Tauria, T. Wankow in 1910 (US); prope Lenkoran,

Azerbaijan, R. F. Hohenacker in 1838 (G, US).

P. cambessedesii, P. corsica, P. coriacea and P. Wittmanniana

These species, with the follicles attenuate at the apex into an elevated stigma, and therefore of the same shape as those of P. albiflora and P. obovata, but with the leaves and sepals characteristic of P. corallina, are apparently closely related, although most of them are widely separated geographically. The only diploid represented is P. Cambessedesii Willk. (Pl. Hisp., 3:976) (cf. Dark, 1936), a native of the Balearic Islands. the only characteristics known to the writer which distinguish this species from the more widespread tetraploid form, P. Corsica Sieb (ex Tausch., Flora, 11:88,1828) are the deep purple color of the under side of the leaves, the larger number of follicles (5 in Cambessedesii, 2-3 in Corsica), and the strongly rather than moderately wrinkled seed coat. No herbarium specimens of this type with a stomatal size indicating the diploid number have been seen. The following are all apparently tetraploid. Those from Majorca agree well with descriptions of P. cambessedesii, the others with P. Corsica.

Majorca: Ombre, rare, Knocks no. 116 (Kn); Faro Formentor, Knachc no. 122 (Kn).

Corsica: Serra de Scopamene, par Sartene, IS. Reverchon no. 218 (as P. Russi, Kn).

Sardinia : Monte Limbardo, arr. de Tempio, E. Reverchon no. 291 (part, as P. Russi, Kn).

Rhodes: Collines dn Mt. San Elio pres de Salakos, E. Bourgcau in 1870 (part, as P. corallina, US).

P. coriacea Boiss, Voy. Esp., 14 t. 3, 1838.

This plant, from Spain and Morocco, appears very distinct in its glaucous habit, large follicles, and elongate stigmas, but may be only a well-marked variety of the preceding. The following specimens, all apparently tetraploid, have been seen:

Spain: Puerto del Viento, Sierra de Ronda, E. Bourgeon in 1849 (Q). Prov. Malacitana, Kegnum Gpanatense, Huter, Poria et Kigo no. 862 (Kn).

Morocco: Djebel Cilliatin, prov. de Demnat, Ibrahim in 1879 (0); Yebel Tisuka, alt. 1800 m., Font Quer. no. 105 (as P. mascula var. muroccana, VC); supra Azrou, 1500 m., R. Maire in 1933 (DC,).

Algeria: Djebel Majlis, 1600 m., Reverchon no. 324 (Kn).

P. Wittmanniana Hartwiss (ex Lindl.) Bot. Reg., n.a., 9: t. 9, 1846); Stev. in Bull. Soc.

Nat. mobc., 21:2, 275,1848. P. Willmottiae Stapf., Bot. Mag., 142: t. 8667, 1916.

Finet and Gagnepain (1904) first pointed out that the plants of western China then passing as P. obovata Maxim, were actually indistinguishable from P. Wittmanniana Stev. of Persia. Stapf did not take their publication into account in his description (1. c.) of these Chinese plants as P. Willmottiae, nor did he compare his proposed species with P. Wittmanniana, although he rightly pointed out its distinctness from true P. obovata of northeastern China, Manchuria, Korea, and Japan, a point on which Finet and Gagnepain were doubtful. The only distinction between the Persian and Chinese forms which the writer can find is in the color of the flowers, which in Wittmanniana is pale yellow, in obovata, white. The localization of P. Wittmanniana in northern Persia and western China gives it the most extraordinary range of any species of the genus. This is made even more remarkable by the close affinity of P. Wittmanniana not only to P. obovata, but also to P. Corsica and P. coriacea of the Mediterranean region. Phylogenetieally, these species are the most advanced of the genus. The strictly 1-flowered habit, the reduced number and specialized shape of the sepals, and the wrinkling of the seed coat are all specializations not found in the more primitive species of the subgenus, such as P. anomala and P. albiflora. Furthermore, their tetraploid nature indicates that they are of more recent origin than other species, such as P. triternata and P. obovata, which have similar morphological specializations. Nevertheless, their disrupted ranges and localized occurrence suggests that even these species are very old chronologically, and therefore that the entire genus is an extremely old one. The following specimens are typical of P. Wittmanniana:

Persia: prope Siaret, in montis prov. Astrabadensis, Runge in 1858 (G).

China : IIupeh, without definite locality, A. Henry nos. 847,5365 A (G, NY); western Hupeh, E. H. Wilson no. 359 (C). Shin Shan Hsien, Hupeh, W. Y. Chun and S. .S. Chien no. 835 (UC); Nanchuan-hsien, Szechuan, 1820-2120 m., W. P. Fang no. 1081 (G).

P. obovata Maxim, Prim. Fl. Amur., 29,1857. P. japonica Miyabe and Takeda, Gard. Chron., 48:366, 1910.

This species is a most distinctive one, not only in its low habit, small flowers, and slender peduncles, but also in its floral characteristics. The sepals, reduced to three in number and completely devoid of foliaceous appendages, are the most advanced in the genus. The narrow, acute petals also show specialization in being more sharply differentiated from the sepals than in most of the species. Phylogenetieally, P. obovata may be considered the most advanced of all the diploid species of Paeonia. the characters on which Miyabe and Takeda separated the Japanese form from that of Korea, northern China, and Manchuria have not been found to hold. The stigma illustrated in figure 13, c is from Japanese material, but is quite similar to that found in Manchurian and Korean specimens, some of which have the undersurface of the leaves glabrous, a characteristic used by its authors to distinguish P. japonica. The following specimens are typical:

China : Chihii, without locality, Chanet in 1918, no. 30 (G); near eastern tombs Hopei (Chihii), K. M. Liow.

Manchuria; Inter fluv. Tsutar et Tala-acz, 7. Komarov no. 654 (G, NY).

Korea : In silvis Hallaisan, IJ. Faurie no. 1711 (UC).

Japan: Sapporo, K. Sugiyama in 1885 (NY); southern Hokkaido, without definite locality, W. P. Brooks nos. 437,551 (UC).

The writer is much indebted to Dr. A. P. Saunders for valuable assistance throughout this work, and to Mrs. Katherine D. Jenkins for the execution of the drawings.


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Fig. 1. The aeeda (x 2) and the surface markings on the seed coats (x 100) of: A, Paeonia Delavayi var. lutca; B, P. albtflora; c, P. anomala Woodwaraii; D, P. tenui-folia; E, P. trilcmaia Miokosewitschii; r, P. otovata.