Bull. Natl. Mus. Nat. Sci., Ser. B, 41(1), pp. 15–24, February 20, 2015

Updates of Taxonomic Treatments for Ferns of Japan 1.
Botrychium, Osmolindsaea and Pteris
Atsushi Ebihara1,*, Narumi Nakato2 and Sadamu Matsumoto1
1

Department of Botany, National Museum of Nature and Science,
Amakubo 4–1–1, Tsukuba, Ibaraki 305–0005, Japan
2
Narahashi 1–363, Higashiyamato-shi, Tokyo 207–0031, Japan* E-mail: ebihara@kahaku.go.jp(Received 11 November 2014; accepted 24 December 2014)

Abstract Reﬂecting the results of recent studies on Japanese ferns, some new taxonomic treatments are proposed including three new hybrid taxa, Botrychium×silvicola (＝B. atrovirens×
B. japonicum), Osmolindsaea×yakushimensis (＝O. japonica×O. odorata) and Pteris×
pseudosefuricola (＝P. cretica×P. multiﬁda).
Key words : Botrychium, ferns, hybrids, Japan, Osmolindsaea, Pteris.

Japan is considered as one of the mostadvanced areas in studies of fern ﬂora (e.g. Iwatsuki et al., 1995), and even nowadays it has
been updated continually by additions of new
taxa, especially interspeciﬁc hybrids. We propose
some new taxonomic treatments for the ﬂora toﬁt the names to their biological entities inferredfrom morphological, cytological or molecularevidences.
1. A new hybrid combination for Botrychium(Ophioglossaceae)
Sceptridium japonicum (Prantl) Lyon var.
silvicola Sahashi was originally described from
Oshima Island (Sahashi, 1983a), Tokyo, Japan.
The author, commenting that this taxon is a probable hybrid between S. japonicum and S. atrovirens (Sahashi) M.Kato from the viewpoint of its
habitat and gross morphology, described it as avariety, not a hybrid probably because it produces normal tetrahedral spores (Sahashi, 1983b).
Based on the results of our nuclear DNA analyses (A. Ebihara and Y. Watano, unpublished) thatshowed its genotype is a combination of uniquealleles in S. japonicum and S. atrovirens, it is better to be treated as a hybrid taxon in accordancewith the presently accepted species concept thatrecognizes the two hexaploid parental lineages as
independent species (Sahashi, 1979). At the
moment, it is uncertain whether the spores are
truly fertile or sterile but with normal external
shape, and testing the viability of spores in thegroups producing mycotrophic gametophytes istime-consuming (Whittier and Peterson, 1984;
Takahashi and Imaichi, 2007), but, none the less
it is worthwhile to clarify the grounds for apparent fertility of this 'hybrid' taxon, and also theboundary of species in predominantly inbreeding
ferns (Watano and Sahashi, 1992).
Botrychium×silvicola (Sahashi) Ebihara, stat.
nov.
— Sceptridium japonicum (Prantl) Lyon var. silvicola Sahashi, J. Jpn. Bot. 58: 241, Fig. 1B &Fig. 2, 1983. — Botrychium japonicum (Prantl)
Underw. var. silvicola (Sahashi) M.Kato, Fl. Jap.
1: 26, 1995.
Jap. Name: Gojinka-hanawarabi.
Distribution: Tokyo Metropolis, Izu Islands.

Atsushi Ebihara et al.

16

Fig. 1. Holotype of Osmolindsaea×yakushimensis Ebihara et Nakato (N. Nakato 1018, TNS [VS-469765],
voucher of chromosome count 2n = 235, pentaploid). A: the whole sheet (scale bar = 5 cm); B: fertile lamina(scale bar = 1 cm).

Taxonomic Treatments for Ferns of Japan 1

Fig. 2. Osmolindsaea×yakushimensis in Yakushima
Isl., growing on moist, stream-side rocks (photograph by T. Oka in April 2013).

2. A new hybrid of Osmolindsaea (Lindsaeaceae)
Osmolindsaea odorata (Roxb.) Lehtonen et
Christenh., the type species of the recently established genus Osmolindsaea (Lehtonen et al.,2010) is distinct from O. japonica (Baker)
Lehtonen et Christenh., a closely related taxon
often placed at its varietal rank, in ploidy level —i.e. O. odorata is hexaploid (n＝150, Manickam
and Irudayaraj, 1988; n＝155, Kurita, 1962) andO. japonica is tetraploid (n＝ca. 80, Mitui, 1976;
n＝ca. 75, 2n＝ca. 150, Lin et al., 1990). In
Yakushima Isl. in southern Japan, where the two
species sometimes grow nearby, morphologicallyintermediate forms are observed. The voucher
specimen of pentaploid “O. odorata” by Nakato(1987) best matches the intermediate forms, andthe ploidy level is intermediate accordingly. We
concluded that this is an interspeciﬁc hybrid
between O. japonica and O. odorata. The presence of this hybrid or intermediate form has beensuggested several times (e.g. Nakaike, 1982;
Lehtonen et al., 2013) but this is the ﬁrst record
with an obvious citation of specimens.
Osmolindsaea×yakushimensis Ebihara et Nakato,
hybr. nov. (Figs. 1, 2)
Jap. Name: Koke-hongu-shida (ﬁrst appeared17

in Sugimoto [1966]).
Differs from O. japonica in its frequently
interrupted sori, and from O. odorata in its
smaller frond sizes and stream-side habitat. Produces irregular spores.
Typus: JAPAN. Kagoshima Pref., Yakushima
Isl., Hanaage-gawa River. 1981-12-18. N. Nakato
1018, voucher of chromosome count 2n＝235(holo-TNS [VS-469765]).
Distribution: Japan (Yakushima Isl.) and possibly in Taiwan (Lehtonen et al., 2013).
Habitat: On moist, stream-side rocks, not very
close to the water surface as in O. japonica.
A pentaploid hybrid between O. japonica andO. odorata. Rhizomes short creeping, densely
covered with brown scales, ca. 0.5 mm long, 1–4cell wide at bases, bearing fronds at intervals of
0.5–1 cm. Stipes stramineous to purplish withdarker bases, 2–4 cm long. Laminae lanceolate inoutline, 5–10×1.2–2.0 cm, 1-pinnate. Lateralpinnae 12–17 pairs, shortly stalked, dimidiate,
0.6–1.0×0.3–0.5 cm at middle portion, often signiﬁcantly shortened at basal parts. Sori marginal,
interrupted, forming 2–6 oblong ones per pinna.
Note: The frond shape and size in general aresimilar to those of larger individuals of O. japonica, but the marginal sori are often interrupted asin O. odorata.
Additional specimens examined: Japan.
Kagoshima Pref., Yakushima Isl., Nakase-gawaRiver. 1973-3-27. H. Miyazaki s.n. (TNS [VS806058]).
Identity of ʻPteris×sefuricolaʼ (Pteridaceae)
Though not yet published validly, the name
ʻPteris×sefuricola Sa. Kurataʼ has been widelyused as a name for the interspeciﬁc hybrid
between P. cretica L. and P. multiﬁda Poir. (e.g.
Kurata and Nakaike, 1994, 1997; Iwatsuki et al.,1995). The plant was ﬁrst noticed by Mr. S. Tsutsui at Kanayama, Sawara-machi, Fukuoka Prefecture located in the Sefuri Mountain Range,
and was later recorded throughout the mainland
Japan (Kurata, 1977). Its partly winged rachis isclearly intermediate between the two parental
species, but a degree of infraspeciﬁc variation3.

18

Atsushi Ebihara et al.

has been known, including variation in the veincharacter of the sterile lamina (for example every
vein reaches the margin in some individuals but
veins terminating short of the margin are mixed
in others) and the ratio of the production of normal spores (for example all spores are normal insome individuals but mostly abortive or irregular-shaped in others). Although Kurata (1977)
denied correlation between the vein characterand the ratio of normal spores, Yamazumi (1989)
successfully grouped ʻP.×sefuricolaʼ individuals
collected in Minoh, Osaka Pref. into two types,
namely, the “M-type” and the “C-type”. The“M-type” had veins not reaching the margin andproduced mostly irregular-shaped spores, whilethe “C-type” had veins reaching the margin andproduced normal spores by apogamous reproduction. We also observed that all the specimens,
whose veins were conﬁrmed to reach the margin,
produced only normal spores. These observations
suggested that ʻP.×sefuricolaʼ represents a mixture of two different biological entities rather
than a complex with clinal variation. All known
traits of the “M-type” are well explained by combining those of P. cretica and P. multiﬁda; its tetraploidy probably originated from fertilization
between a reduced diploid egg of sexual tetraploid P. multiﬁda and an unreduced diploid
sperm of apogamous diploid cytotype of P. cretica. Although both Kurata (1977) and Yamazumi(1989) hypothesized that the “C-type” is stabilized progenies of the “M-type”, the “C-type”, anapogamous diploid (2n＝58, Yamazumi [1989]),
is not cytologically identical with the tetraploid“M-type” (2n＝116, Nakato, 1975; Matsumoto[1976]). Alternatively, a more natural hypothesis
would be that the “C-type” is an extreme form of
P. cretica with well developed wings of rachis.
This hypothesis is supported by our molecular
data, which showed that chloroplast rbcL-a
sequences (700 bp) of a “C-type” individual collected in Shirada, Higashiizu-cho, Shizuoka Pref.
(TNS [VS-1225892]) is identical to two of thoseof P. cretica (AB697620, AB697621, Jaruwattanapan et al., 2013). In other words, the maternal
parent of the “C-type” is not P. multiﬁda but

P. cretica.
Keys to the plants formerly identiﬁed asʻP.×sefuricolaʼ
1a. Veins of sterile fronds usually not reachingcartilaginous margins. Spores mostly irregular,
sometimes almost normal. . . . . . . . . . . . . . . . . . . . . . . . P.×pseudosefuricola
1b. Veins of sterile fronds always reaching cartilaginous margins. Spores normal. . . . . . . . . P. cretica (a winged form) [Figs. 3, 5a]
Pteris×pseudosefuricola Ebihara, Nakato et
S.Matsumoto, hybr. nov. (Figs. 4, 5b)— Pteris×sefuricola Sa.Kurata, nom. nud., p.p.
Jap. Name: Ai-inomotoso.
Differs from Pteris cretica in having veins notreaching cartilaginous margins in sterile lamina.
Typus: JAPAN. Tokyo Metropolis, Shinagawa-ku, near the Embassy of Burma, early September, 1970. S. Matsumoto 2326 (holo-TNS[VS-1220664]).
Plants originated from hybridization between
P. cretica and P. multiﬁda. Rhizomes short creeping or ascending, bearing linear, brown scales, up
to 5 mm long. Fronds more or less dimorphic.
Stipes stramineous, sometimes brownish, 10–70 cm long in fertile ones, 10–55 cm long in sterile ones, bearing sparse hairs. Fertile laminae
ovate to lanceolate in outline, 15–45×10–40 cm,
1-pinnate, papyraceous, pale green, terminal pinnae 10–40×0.6–1.5 cm, lateral pinnae 2–5 pairs,
lowest ones often bilobed, 7–30×1.7–22 cm,
segments 0.5–1.4 cm wide, base of the ﬁrst
(uppermost) pair of lateral pinnae decurrent
toward rachis at least halfway to the second lateral pinnae, base of the second pair of lateral pinnae decurrent toward rachis slightly, lower pinnae short-stalked, margins dentate at sterile parts.
Sterile laminae ovate in outline, slightly smaller
than fertile ones, 10–40×6–30 cm, 1-pinnate,terminal pinna 6–30×1.0–2.3 cm, lateral pinnae
1–5 pairs, lowest ones often bilobed, 6–23×2–
14 cm, segments 0.9–2.0 cm wide, base of theﬁrst (uppermost) pair of lateral pinnae decurrent
toward rachis at least halfway to the second lat-

Taxonomic Treatments for Ferns of Japan 1

19Fig. 3. A winged form of Pteris cretica, a duplicate of the original collection, to which ʻP.×sefuricla Sa.Kurataʼ
was given (S. Tsutsui 779, TNS [VS-1161733]).

Atsushi Ebihara et al.

20

Fig. 4. Holotype of Pteris×pseudosefuricola Ebihara, Nakato et S.Matsumoto (S. Matsumoto 2326, TNS [VS1220664]).

Taxonomic Treatments for Ferns of Japan 1

Fig. 5. Veins at the margins in sterile fronds. A: awinged form of Pteris cretica (S. Tsutsui 779,
TNS [VS-1161733]) with veins reaching cartilaginous margins; B: Pteris×pseudosefuricola(S. Matsumoto 2326, TNS [VS-1220664]) withveins terminating short of cartilaginous margins. Scale bar = 1 mm.

eral pinna, lower pinnae short-stalked, margins
dentate and cartilaginous, veins often terminating
short of the cartilaginous margins. Sori elongate
along margins of pinnae, covered by false indusia.
Note: We examined a duplicate specimen of
the original material of ʻPteris×sefuricolaʼ
(Kurata, 1977) kindly provided by Mr. S. Tsutsui,and conﬁrmed that its veins reach the margins:
i.e. it is a winged form of P. cretica. We thenexplored additional specimens from Sefuri
Mountains where the original material was collected. As a result, we found out that all the collections
obtained
from
the
area
as
ʻPteris×sefuricolaʼ were actually P. cretica. This

21

observation indicates that it is difﬁcult to validate
the name ʻPteris×sefuricolaʼ for the hybrid
taxon — ʻP.×sefuricolaʼ is not present in the
Sefuri Mountains. Here, we provide a new epithet for the hybrid to avoid etymological confusion.
Both triploid (Nakato and Hyodo, 2011) andtetraploid cytotypes (Nakato, 1975; Matsumoto,1976) are known, and the former is known only
from Ehime Prefecture (Nakato and Hyodo,2011). Molecular analyses by Jaruwattanaphan etal. (2013) suggested that the tetraploid cytotype
originated from hybridization between P. cretica
and P. multiﬁda, but the origin of triploid has
been unresolved. The tetraploid can produce normal shape spores only at a low ratio (ca. 5%), but
the normal spore germinates, and the resultant
gametophyte can form sporophyte by apogamy(Nakato, 1975). While the triploid produced normal spores at a higher ratio (ca. 90%) (Nakato
and Hyodo, 2011).
Additional specimens examined. JAPAN.
Gunma Pref. Tano-gun, Yoshii-machi, ShioHigashiya, 1980-12-28, T. Waku 10513 (TNS
[VS-1192025]). Saitama Pref. Chichibu-gun,
Minano-machi, Kanezawa, 1983-10-31, T. Iwata
2376 (TNS [VS-932216]). Tokyo Metropolis.
Ome-shi, Sawai, 1973-9-?, N. Nakato s.n. (TNS
[VS-328656], voucher of Fig. 1 of Nakato[1975], TNS [VS-328658], voucher of Fig. 3 ofNakato [1975]), 1973-3-10, N. Nakato s.n. (TNS
[VS-328663], ʻsample no. 5ʼ, TNS [VS-328864]
ʻsample no. 6ʼ, voucher of Nakato [1975]); Shinagawa-ku, near the Embassy of Burma, cultivatedstock of Tsukuba Botanical Garden [TBG79443],
S. Matsumoto 70-8-1 (TNS [VS-1179254] tetraploid, voucher of Jaruwattanaphan et al., 2013).
Shizuoka Pref. Numazu-shi, Washizu-san, cultivated stock of Tsukuba Botanical Garden[TBG126793], T. Hosokura SM990731-30 (TNS
[VS-1179256], tetraploid, voucher of Jaruwattanaphan et al., 2013); Kamo-gun, Kawazu-cho,Nashimoto, cultivated stock of Tsukuba Botanical Garden [TBG126794], T. Hosokura
SM990731-31 (TNS [VS-1179255], tetraploid,
voucher of Jaruwattanaphan et al., 2013). Aichi

22

Atsushi Ebihara et al.

Pref. Chita-gun, Minamichita-cho, Ohi, 1986-216, K. Inukai 7603 (TNS [VS-944208]); Hazugun, Isshiki-cho, Tsuigome, 1990-10-25, K. Inukai 10620 (TNS [VS-944209]); Toyohashi-shi,
Ishimaki-san, 1977-12-10, T. Waku 8175 (TNS
[VS-1192026]). Mie Pref. Inabe-gun, Fujiwaracho, Nishinojiri, foot of Mt. Fujiwara-dake, alt.
150 m, 1985-6-22, F. Miyamoto s.n. (TNS [VS808092]); Hokusei-cho, Tashida Valley, 1976-1211, T. Waku 5654 (TNS [VS-1192027]); Suzukagun, Seki-cho, Kabuto Pass — Fudo-taki Fall,
1975-11-9, H. Miyazaki 4204 (TNS [VS808113]); Owase-shi, Mikisato, Yasogawa, 19883-6, K. Ohora 18686 (TNS [VS-9508457]); Kitamuro-gun, Kii-nagashima-cho, Ohara, Mukai,
1991-3-7, Y. Higuchi s.n. (TNS [VS-944214]).
Osaka Pref. Minoh-shi, Minoh Park, 1976-10-17,
T. Oka s.n. (TNS [VS-1102029]). Wakayama Pref.
Higashimuro-gun, Kumanogawa-cho, Shiko-dani,alt. 150 m, 1991-11-24, K. Seto 37615 (TNS [VS723612]). Okayama Pref. Kibi-gun, Showa-cho,
Yandani, 1977-2-12, T. Nakaike s.n. (TNS [VS944227]). Yamaguchi Pref. Saba-gun, Tokujicho, under Sabagawa Dam, 1992-8-17, A. Minami 82764 (TNS [VS-944164]); Iwakuni-shi,
Akadani, 1992-3-2, A. Minami s.n. (TNS [VS944173]). Ehime Pref. Shikokuchuo-shi, Doicho, Ohkawa, 2003-4-12, S. Hyodo 10711 (TNS
[VS-1192023]); Kita-gun, Uchiko-cho, Ikazaki,
Fukuoka, 2009-2-23, S. Hyodo 13721 (TNS [VS1138395], 2n＝87, triploid, voucher of Nakato
and Hyodo [2011]), Shukuma, 1978-11-5, S.
Hyodo 9 (TNS [VS-378871]); Iyo-shi, Futamicho, Kaminada, Ohe, 2008-12-14, S. Hyodo
13483 (TNS [VS-1192020]; Niihama-shi, Hagyu,
2009-12-11, S. Hyodo 14021 (TNS [VS1192021]); Seiyo-shi, Mikame-cho, Minae, 20122-12, S. Hyodo 15699 (TNS [VS-1192022]).
Fukuoka Pref. Tagawa-gun, Kawara-machi, Seto,
alt. 60 m, 1970-12-29, S. Tsutsui 7429 (TNS [VS1192024]). Kumamoto Pref. Aso-gun, Choyomura, Kawayo, alt. 300 m, cultivated stock ofTsukuba Botanical Garden [TBG133346], S.
Matsumoto 01-023 (TNS [VS-1179257], tetraploid, voucher of Jaruwattanaphan et al., 2013);
Kuma-gun, Itsuki-mura, 1974-2-9, N. Sahashi

s.n. (TNS [VS-366901]).
On the type material of Pteris semipinnata
L.
The name Pteris semipinnata L. was describedfrom China and has been usually applied to aplant species widely distributed in Asian tropics.
Its closely related species, P. dispar Kunze waslater described from a material collected inJapan, and is generally recognized as an East
Asian plant ranging from Japan to China. Thislatter species differs from P. semipinnata in thatthe segments are narrower and the veins reachthe margin (tip of teeth) of the frond in its sterile
part. Kuo (1985) synonymized P. dispar under P.
semipinnata after examining the type material of
P. semipinnata in LINN (an image available at
http://linnean-online.org/12507/), and accepted
the name P. dimidiata Willd. for the plant formerly called ʼP. semipinnataʼ. However, his treatment has been followed by only a small numberof subsequent Taiwanese publications, and the
traditional treatment has been maintained in mostof the recent ﬂora of East Asia (e.g. Japan [Iwatsuki et al., 1995], China [Zhang et al., 2013] andTaiwan [Knapp, 2011]). Fraser-Jenkins (2008)
also advocated the traditional treatment based on
his identiﬁcation: the type sheet of P. semipinnata was considered a mixture of two species,
namely ʻP. semipinnataʼ in the traditional sense(the right-handed frond) and ʼP. disparʼ in the traditional sense (the left-handed frond). The basisof his identiﬁcation of the left-handed frond as ʼP.
disparʼ was its developed acroscopic lobes. However, the degree of acroscopic lobe development
is variable in ʼP. disparʼ (Nakato, 2012) and two
fronds of the type sheet undoubtedly fall into therange of ʼP. disparʼ. This justiﬁes Kuo (1985)ʼs
opinion and therefore we can no longer apply thename P. semipinnata in the traditional sense, andP. semipinnata should be used as the correctname for the plant formerly called ʻP. disparʼ. On
the other hand, the suggestion by Fraser-Jenkins(2008) that “Kuo overlooked the earlier name
Pteris alata Lam., which also applies to P. semipinnata” is also justiﬁed and here we accept
4.

Taxonomic Treatments for Ferns of Japan 1

Pteris alata Lam. as the correct name for ʻP.
semipinnataʼ in the traditional sense instead of P.
dimidiata.
Pteris alata Lam., Tabl. Encycl. t. 869, 1799.
Pteris dimidiata Willd., Sp. Pl. 5: 381, 1810.
Pteris semipinnata auct. non L.
Jap. Name. O-amakusa-shida
Distribution. Throughout E Asia, SE Asia andS Asia.
Pteris semipinnata L., Sp. Pl. 2: 1076, 1753.
Pteris dispar Kunze, Bot. Zeit. 6: 539, 1848.
Jap. Name. Amakusa-shida
Distribution. Japan, Korea, China and Taiwan.
Acknowledgments
We are grateful to S. Tsutsui for providing
specimens of ʻPteris×sefuricolaʼ and T. Oka forproviding a photograph of Osmolindsaea×
yakushimensis. This study was partly supported
by JSPS KAKENHI (Grant no. 24770083 toA.E.).
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