glabrous; leaflets 3-7, the terminal one often partially to deeply divided, lanceolate, 8-15 mm long, 5-7 mm broad, the terminal up to 25 mm long, base acute, sessile, or broadly merging with the rachis, apex acute, the terminal leaflet subacuminate to acuminate. Inftorescence terminal on side- shoots, 3-5-flowered, glabrous, the 2 lower flowers in the axils of a pair of leaves, the others subtended by 2 bracts, leafy to subulate, pedicels approximately equal, 1.5-2.5 cm long. Flowers long-styled, sweetly scented. Calyx glabrescent, tube c. 3 mm long, lobes 5, linear, acute, 4-5 mm long. Corolla-tube 14-15 mm long, almost cylindrical, slightly wider at the top, c. 2.5 mm wide, lobes 5, imbricate in bud, patent to slightly reflexed at anthesis, broadly ovate to orbicular, 7-9 mm long, apex rounded with a small apiculum, the tube, and the back of the lobes that formed the exterior of the bud, bright red, the remainder pure white. Stamens 2, epipetalous, inserted about the middle of the corolla-tube; filaments c. 1 mm long; anthers c. 4 mm long. Ovary somewhat globose, c. 1 mm in diameter, style c. 12 mm long. Fruit not known.

DISTRIBUTION (of the species). Caucasus, N Iran, Pakistan, Himalaya to SW China.

REFERENCES

Carricre, E. A. (1878). Jasminum affine. Rev. Hort. 50: 427428. Green, P. S. (1986). Jasminum in Arabia; studies in the genus Jasminum

Kubuski, C. E. (1932). Synopsis of the Chinese species of Jasminum. J .

Lindley, J. (1845). Jasminum afine. Edwards’Bot. Reg. 31: t. 26. Linnaeus, C. (1 762). Species Plantarum (edn. 2). Stockholm. Nicolson, G. (1885). Illustrated Dictionary o f Gardening Vol. 2. London. Rehder, A. (1949). Bibliograpb o f Cultivated Trees and Shrubs. Boston.

L. (Oleaceae): X. KewBulE. 41: 413-418.

Am. Arb. 13: 145-179.

TWO JAPANESE SPECIES OF ASARUM

Peter Boyce

The exact status of the genus Asarum L. (Aristolochiaceae) in Japan is problematic. In the past some botanists have recognized a number of segregate genera separated from Asarum sensu strict0 by relatively minor characteristics of the flower (e.g. Heterotropa Morren & Decaisne, 1834) separated by the presence of a distinct floral tube and free styles with lateral anthers, Japonasarum Nakai (1936) recognized by the strongly reflexed perianth-lobes, Asiasarum Maekawa (1936) separated by the stamens being inserted on the

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ovary and Geotaenium Maekawa (1953) removed from Asarum sensu stricto on the basis of the chromosome count of 2n = 12 (2n = 24,26 in Asarum sensu stricto) and because of the presence of a rudimentary ‘corolla’ - actually a ring of staminodes). This tendency to split has extended to the United States where Hexastylis Raf. (1825) has been separated from Asarum (see Boyce & Stannard, 1988). More recently the trend towards the recognition ofsegregate genera in Asia has been reversed, with various authors (e.g. Cheng & Yang, 1983; Hatusima & Yamahata, 1988) reverting to the concept of a single genus with a number ofsubgenera, sections and series. A detailed discussion can be found in Yinger ( 1983).

197. ASARUM FUDSINOI

Asarum fudsinoi T. Ito was described in 1924 from material collected on Amami-Oshimi island, one ofJapan’s southernmost Ryukyu Islands. Vegetatively it is one of the largest and most handsome members of the genus. Although its flower colour is rather undistinguished when compared with someofits moreshowy Japanesecounterparts, such as A. yakushimense Masamune ( 1933), the pale yellowish green and reddish purple blossoms make up in size what they lack in colour and, combined with the distinct foliage, give a singularly attractive impression.

Asarum fudsinoi did not escape the attention ofthe ‘splitters’ and the name Heterotropa fudsinoi (T. Ito) Maekawa ex Nemoto (Nemoto, 1936) is still widely used in Japanese works. The first plant of A. fudsinoi that arrived at Kew was labelled Heterotropa fudsinoi var. gigantea F. Maekawa (Yuasa & Maekawa, 1976). The differences used to separate this andvar.yanmaF. Maekawa (Yuasa & Maekawa, 1976) from the typical plant appear to be relatively insignificant and, given the variability ofA. fudsinoi in the wild, are not accepted here.

Recently, another specimen ofthis plant arrived at Kew donated by Osaka University Botanic Gardens from material cultivated there. This second accession bears the cultivar name ‘Fujinokanaoi’. Vegetatively the plant appears to be more or less identical to the form described here. I t remains to be seen how the flowers differ from those of the typical plant.

CULTIVATION. The plant illustrated here was received as a small offset by Tony Hall of the Alpine Department at Kew, from Takemi Iida, a former Kew student. The plant proved to be too vigorous for pot culture but, coming from so far south in Japan, was too tender to

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Asarum fudsinoi

Plate 197

ANN FARRER

grow outdoors in London. Furthermore, choice Asarum species planted outside have proved to be attractive to unscrupulous collectors in the past and have sometimes been stolen.

The offset was planted adjacent to the pond and waterfall in the Alpine House at Kew in 1981. This situation takes advantage of the cooler microclimate in this section ofthe house but allows the plant to enjoy almost full sun. Nevertheless, the house is lightly shaded with Varishade in sunny weather. The compost is a deep, peaty, leafy, sandy soil which never dries out. The Alpine House is kept at about 2°C during cold weather and although this is certainly lower than the temperatures which the plant would encounter in nature, no ill-effects have been apparent. Since it was planted A. fudsinoi has increased magnificently to form a bold clump of large, glossy, evergreen leaves. An individual leaflasts two or three years; old, damaged leaves are re- moved during early winter to enable the newly emerging leaves to expand.

Although A.fudsinoi grew well, it did not flower until 1990. It appears that it requires a warm summer to encourage it to blossom. Once in flower, a succession of blooms continued for some months. Unfortunately, as in many ofthe evergreen Asarum species, most ofthe flowers were concealed beneath the leaves. However, the outermost flowers were clearly visible and very impressive.

Most Asarum species are relatively easy to grow. However, aphids can distort the foliage badly, particularly if an infestation establishes itselfon newly emerging leaves. Aphids also pose a threat in transfer- ring viruses between plants and it is important that measures should be taken to control them. Leafscale can be an occasional problem and should be dealt with immediately by dabbing with methylated spirits. I n addition the larvae ofvarious moths, particularly ‘tortrix’ (Tortrix pronubana) can cause considerable, even permanent, damage to leaves. Fortunately, A. fudsinoi appears to be unattractive to slugs, which can cause so much damage to other species.

The leaves should be regularly cleaned which not only improves the appearance ofthe plant, but keeps the foliage clear ofdust and calcium deposits and this is beneficial to the plant’s general health.

Asarum fudsinoi has proved easy to propagate by division of the rhizomes. Small outer portions can readily be removed with a few roots and potted individually. The abundant floweringin 1990 did not produce seed and it seems possible that two genetically distinct plants are required to ensure seed production.

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Asarum fudsinoi T. Ito in Sci. Rep. Tbhoku Imp. Univ., Ser. 4, Biol. 1 : 45 (1924). Type: Japonia australi: in vallibus montanis prope portum Naze, insulae Amami-Oshima, 3 November 1906 (sterile) Fudsino sm., 5 January 1907 (flowering) Fudsino s.n. Although Ito cites two collections, he clearly states that the illustration accompanying the protologue was prepared from Fudsino’s fertile material. Thus, the second collection listed above is the holotype (holotype TNS n.v., isotype TNS n.v.) Heterotropa fudsinoi (T. Ito) Maekawa ex Nemoto, FI. Jap., Suppl., 1107

Asarum fudsinoi T. Ito var. giganteum F. Maekawa in La Kromosomo 2: 10

A.fudsinoiT. 1tovar.janma F. Maekawa, loc. cit. Type: Ryukyu Is. (holotype

(1936).

(1976). Type: Ryukyu Is. (holotype not traced).

not traced).

DESCRIPTION. Evergreen, rhizomatous aromatic herb forming clumps up to 50 cm in diameter. Rhizome slightly dorsi-ventrally compressed-terete, branching repeatedly to form a dense mat, rooting adventitiously from the lower surface, 1-7 cm long, 5-7 mm wide, off-white, greenish brown where exposed. Leaves elliptic-cordate, acute, posterior lobes rounded, inner margins over-lapping slightly, 9-24 cm long, 6-13 cm wide, deep green above, markedly paler with purplish brown primary veins beneath, glossyon first emerging, later becoming semi-glossy and finally rather matt. Petioles

Asarum fudsinoi, habit. Drawn by Ann Farrer.

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Asarum fudsinoi. A, half-flower, X 3; B, flower, view from above, X 3%. Drawn by Christine Grey-Wilson.

terete, 12-37 cm long, 3.3-11 mm wide, mid-green, k evenly suffused with purple brown. Flowers borne singly, rarely 2 or 3 together, subtended by 3 bracts, 1-2.5 cm long, 1-1.5 cm wide, elliptic, acute, pale green, f suffused with purple brown. Pedicel terete, 1-2 cm long, 2- 3 mm wide, pale greenish brown, suffused with purple-brown. Perianth 3.5- 5 cm in diameter, slightly unequally 3-lobed, lobes broadly ovate to subdeltoid, obtuse to subacute, spreading, exterior pale yellowish to deep olive-green, suffused and spotted with reddish purple, interior pale greenish yellow suffused with mid-purple, fading to pale greenish cream towards the throat, c. 1.5 cm long and 1.5 cm wide, perianth-tube 2-3 cm long, exterior smooth, pale yellowish to olive-green, interior strongly reticulate, reddish purple. Anthers subsessile, oblong, obtuse, minutely appendiculate, 4-5 mm long, 0.75-1 mm wide, deep velvety purple. Stigma ovate, 1.5-2 mm long, deep purple, style thick, 2-lobed, 6-8 mm long, c. 0.75 mm wide, deep purple. Ovary hemispherical, c. 7 mm in diameter, purple. Seed not known.

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DISTRIBUTION. S Japan: Ryukyu Islands, Amami-Oshima Is.

REFERENCES

Boyce, P. C. & Stannard, B. (1988). Hexastylis speciosa. Kew Mag. 5: 151-

Cheng, C. & Yang, C. (1983). A synopsis of the Chinese species ofAsarum

Hatusima, S. & Yamahata, E. (1988). Illegitimately Published Taxa of

Ito, T . (1924). Asarum fudsinoi, in Sci. Rep. T6hoku Imp. Univ., Ser. 4, Biol. 1:

Maekawa, F. (1936).Asiasarum. InNakai,T., Fl.S_Ylv. Koreana21: 16.Keijo. - (1 953). Geotaenium. Proc. VZZ Paczjc Sci. Congr. 5: 2 17. Masamune, G. (1933). Beitrage zur Kenntnis der Flora von Sudjapan.

Morren, C. & Decaisne, J. (1834). Heterotropa. Ann. Sci. Nut. 2: 314, t. 10. Nakai, T. ( 1936). Japonasarum. Fl. Sylv. Koreana 2 1 : 17. Keijo. Nemoto, K. (1936). Heterotropa fudsinoi. Fl. Japan Suppl., 1107. Tokyo. Rafinesque, C. S. (1825). Hexastylis. Neogenyton, 3. Lexington. Yinger, B. R. (1983). ‘A horticultural monograph of the genus Asarum,

sensu lato, in Japan’. M.Sc. (Hort.) thesis. University of Delaware. Yuasa, H. & Maekawa, F. (1976). Chromosomes of Asarum and

Heterotropa (Aristolochiaceae) in the Ryukyu Islands. La Kromosomo 2: 8-18.

153.

(Aristolochiaceae). J. Am. Arb. 64: 565-597.

Asarum from Japan. J . Phytogeogr. Taxon. 36: 1-8.

45.

Trans. Nut. Hist. Soc. Taiwan 23: 204-210.

198. ASARUM MINAMTTANIANUM

Described in 1970, the Japanese Asarum minamitanianum is unquestion- ably one of the most unusual species in a genus notable for its singular flower structure.

Asarum minamitanianum was first received at Kew in 1986 via the late Gerry Mundey from Don Ellick, an American living in Japan and deeply interested in its flora. His stock probably came from a nursery or private collection, because A. minamitanianum is considered to be extinct in the wild (Yinger, 1983). Asarum minamitanianum appears to have had a restricted distribution and to have been on the verge of extinction when it was discovered. The activities of collectors have since completed its extinction in the wild. Many Japanese species of Asarum have similarly limited distributions and are likewise under threat from collectors.

The distinctive appearance of A. minamitanianum in flower means that there is little chance ofconfusing it with any ofthe other Japanese species. Yinger ( 1983), discussing relatives ofA. minamitanianum, lists

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