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(in English) by JISABURO OHWI National Science Museum, Tokyo, Japan

A combined, much revised, and extended translation by the author of his H AS #H @ i& FLORA OF JAPAN (1953) and AH A HE Wy it ~ BS FLORA OF JAPAN—PTERIDOPHYTA (1957)

Edited by

Frederick G. Meyer Research Botanist, U.S. National Arboretum


Egbert H. Walker

Research Associate, Smithsonian Institution



Author’s preface to the English edition Vii Editor’s preface to the English edition ix Introduction 1 Phytogeographical résumé 1 Historical résumé of floristic work in Japan 6 General key to the families 9 Phylum Pteridophyta 21 Phylum Spermatophyta 109 Class 1. Gymnospermae 109 Class 2. Angiospermae 118 Subclass 1. Monocotyledoneae 118 Subclass 2. Dicotyledoneae 359 Reference list of authors’ names 931 Index of Japanese plant names 951 Index of scientific names 984

Index of English names 1067


a ON US ae TS





Osmunda asiatica and Asplenium antiquum

Dicranopteris linearis and Sphenomeris chinensis

Woodwardia orientalis var. formosana and Cyathea boninsimensis Cycas revoluta and Pinus pumila

Picea jezoensis var. hondoensis and Pinus thunbergi

Sciadopitys verticillata and Cryptomeria japonica

Themeda japonica

Miscanthus sinensis and Mount Shibutsu from Ozegahara Moor Livistona subglobosa and Crinum asiaticum var. japonicum Betula platyphylla var. japonica and Callianthemum miyabeanum Stauntonia hexaphylla and Machilus thunbergu

Pittosporum tobira and Rhus javanica

Kandelia candel and Angelica ursina

Helwingia japonica and Rhododendron japonicum

Viburnum plicatum var. glabrum and Hypochaeris crepidioides Trichosanthes bracteata and Farfugium japonicum


Carex kobomugi and Carex macrocephala Japonolirion osense Nakai Calanthe oblanceolata Luisia teres

Nuphar japonicum Corydalis ochotensis Cardamine appendiculata Potentilla matsumurae Euchresta japonica Polygala reinii

Vaccinium sieboldii Primula tosaensis Cynanchum katoi Omphalodes prolifera Salvia japonica

Uncaria rhynchophylla Ligularia stenocephala

Following page 108 108 108 108 108 108 254 D4 254 468 468 650 650 650 854 854

Page 226 282 350 356 436 478 484 526 558 586 711 722 748 758 779 824 880


nay Nite be


She iat



The original Japanese language edition of my Flora of Japan was published in Tokyo in 1953. This work included the in- digenous and adventive spermatophytes but not the pterido- phytes found in present-day Japan. Various authors have pub- lished floras of our realm, the first were by Europeans who visited Japan under Dutch auspices in the 17th, 18th, and 19th centuries. Under the influence of Europeans our own people began to collect plants in earnest after the middle of the 19th century. Soon thereafter the first flora listing all the plants known at that time was published by Jinzo Matsumura in 1884. Since that time other floras have been produced.

My Flora is a culmination of more than 30 years of study. Based largely upon my own field studies, this work is designed as a manual for students and for others less technically trained, who, from time to time, require a reference work to the flora of our islands. The present translation, the only flora of Japan in the English language and the first in a European tongue since Franchet and Savatier’s flora of 1875-79, is an emended and in several respects a revised version of my original work. Inclusion of the pteridophytes (ferns and fern allies), the pho- tographs, and the maps are features of the English version not found in my original Japanese edition. Also included in this English edition are some species recently recorded and not in- cluded in my Japanese edition. The nomenclature in the pres- ent work is in accordance with the International Code (In- ternational Rules Bot. Nom., 1961).

I shall be pleased if this English edition of my Flora is found to be useful to others outside my country. The translation might never have been undertaken except for my acquaintance with Leopold A. Charette of Burlington, Vermont, who, as a member of the U.S. Air Force, collected plants in parts of western Honshu and came to me for assistance shortly after


publication of my flora in 1953. He urged me to prepare trans- lations of certain genera for him, which I did. Very soon thereafter, I accepted the proposal to translate the entire work for publication in English.

I am deeply grateful to Drs. Tetsuo Koyama and Siro Kit- amura for contributing full treatments included here. The former wrote up the Araceae, Eriocaulaceae, and Juncaceae; the latter the Compositae. Much assistance has been generously given by various other Japanese and American botanists. In addition, much of the translation of this English version from my Japanese volume of 1953 was made by Dr. Koyama, a labor for which I am very grateful.

I wish to thank my American sponsors for making this translation of my Flora possible and for their continued and devoted interest over the long period since this translation project began in 1954. The Missouri Botanical Garden, St. Louis, Missouri, sponsored the first two grants-in-aid received from the National Science Foundation, Washington, D.C., for translation in Japan of the Japanese text. A third and final grant, again from the National Science Foundation, together with funds provided by the Smithsonian Institution, made publication possible. Final editing and all arrangements for publication were entrusted to Frederick G. Meyer, Takoma Park, Maryland (formerly of the Missouri Botanical Garden), and Egbert H. Walker of the U.S. National Museum, Smith- sonian Institution, Washington, D.C. (retired). To friends and colleagues in my country I wish to extend thanks for provid- ing photographs which appear in the present work and for assisting me in various other ways.

JisaBurO OWI National Science Museum, Tokyo January 1965

Lbs att

oh we ‘, BN


The flora of Japan first became known to westerners through the agency of the Dutch East India Company, established in Nagasaki in 1609. The first list of Japanese plants published in Europe was the “Amoenitatum Exoticarum” of Engelbert Kaempfer, published in 1712. Europeans under Dutch auspices continued to study the Japanese flora until Japan was opened to world commerce in 1859. Relatively soon thereafter, and continuing up to the present day, Japanese botanists have been busily engaged in the study of their flora.

To agriculturists, foresters, and horticulturists in America and Europe, and in other warm-temperate areas of the world, the Japanese flora long has been an important source of plant materials of economic importance. To botanists, the Japanese flora gained lasting prominence among students of the North Temperate boreal flora with Asa Gray’s now classic paper pub- lished in 1859,* which emphasized the relationships of the Japanese flora to parts of eastern United States.

The flora of Japan is perhaps the best known of any country in eastern Asia. Since about 1868, each period of activity has seen new floristic works published. Floras published in Japa- nese by Jinzo Matsumura, Tomitaro Makino, and Takenoshin Nakai, for example, are well known in Japan, although they have been of relatively little use to western botanists, prin- cipally because of language barriers.

This English language edition of a Flora of Japan, by Dr. Jisaburo Ohwi, is an attempt to bridge the language barrier. The last floristic work to cover the Japanese archipelago in a western language was Franchet and Savatier’s two-volume “Enumeratio Plantarum in Japonia Sponte Crescentium Huc- usque Rite Cognitarum,” published 1875-79. Unlike other floras of Japan of the past, Dr. Owhi’s work is the first to in- clude synoptical keys of all taxa through the level of the spe- cies. With this English translation, botanists, horticulturists, agriculturists, and others not fluent in the Japanese language

+Gray, A. Diagnostic characters of new species of phaenogamous plants, collected in Japan by Charles Wright, Botanist of the U.S. North Pacific Exploring Expedition, with observations upon the re- lations of the Japanese flora to that of North America, and of other parts of the northern temperate zone. Mem. Amer. Acad., n. ser.

6: 377-452, 1859.

have available a modern floristic work of Japan which covers the ferns through the phanerograms. We should point out here that the English language edition of this Flora of Japan is an emended account and not merely a verbatim translation of Dr. Ohwi’s original work in Japanese.

The Romaji or Japanese vernacular names are included for all taxa listed in this English edition, although to westerners the supplying of a vernacular name for every taxon might seem superfluous. This is due to the relative similarity of west- ern languages to Latin, the basis of the scientific names. But to the nonbotanist in Japan there is a far greater need for a ver- nacular name in Japanese because the great difference between that language and Latin precludes the use of the latter by the uninitiated. The vernacular names supplied by the author have been altered by the junior editor, with the aid of Mr. Hisao Matsumoto of the Library of Congress in Washington, D.C., by the insertion of additional hyphens, more than are commonly used by Japanese scholars. In this way the attempt has been made to aid westerners who may be interested in these names to comprehend more readily their structure and meaning. Japanese plants in cultivation often bear the original Romaji name and for this reason inclusion of the Japanese names is justified and useful.

In preparing the manuscript for publication, the editors have at all times endeavored to render faithfully and accurately the full intentions of the author, realizing fully the pitfalls of edit- ing another author’s work. All changes, corrections, and addi- tions have been carefully checked by the author himself. Vari- ous specialists in the United States have offered editorial assistance: Agnes Chase (Gramineae); F. A. McClure (Bam- buseae); C. V. Morton (ferns); Lincoln Constance (Umbel- liferae); Robert E. Woodson, Jr. (Apocynaceae and Asclepia- daceae); Rogers McVaugh (Campanulaceae); F. Raymond Fosberg (Rubiaceae); and S. F. Blake (Compositae). Without the full cooperation and cordial relationships between the edi- tors and the author, this project would not have been possible.

FREDERICK G, MEYER Ecpert H. Waker, Editors

January 1965



In Europe and North America, many exhaustive floristic works are available, but in our country the lack of such works frequently has been keenly felt by us. Most of the early floristic investigations on the Japanese flora, beginning in the 18th cen- tury, were made by Europeans. Serious study and collecting by Japanese botanists began first in the 1860's. The early published works by our own botanists were mostly regional floristic stud- ies, although several floras of the entire Japanese archipelago from time to time have been published. One of the earliest was that of Jinzo Matsumura, “Nippon shokubutsu mei-i,’ pub- lished first in 1884, which went through nine editions. The “Nippon shokubutsu-dzukan” [“Illustrated Flora of Japan”], by Tomitaro Makino, first published in 1925, went through several editions and reprints, the latest in 1963. The “Nippon- shokubutsu-soran” [“Flora of Japan’”], by Tomitaro Makino and Kwanji Nemoto, first published in 1925, was issued the same year as Makino’s Illustrated Flora. The “Nova Flora Japonica,” by Takenoshin Nakai and M. Honda, 1935-51, un- fortunately was never completed.

The writing of my original Japanese edition began in 1947 after more than 30 years’ study on our flora. The aim was to produce a manual for botanists, dendrologists, foresters, and agriculturists, and a guide book for students who require a ready source of taxonomic information about the plants of Japan.

The present work enumerates all spontaneous plants inclu- sive of the ferns and fern allies, gymnosperms, and phanero- gams. Synoptical keys are included for all taxa to the level of the species. A conservative interpretation of the taxa has been attempted. In complex groups, such as Sasa, Aconitum, Hosta, and others, where innumerable microspecies have been recorded by specialists, it has not been possible to include these in my Flora. Trivial variations in flower color, horticultural variants, local aberrations in vegetative morphology, such as dwarfs and monstrosities, are generally excluded. Exceptions to this are in instances where garden plants, long known to us, are enumerated as having originated from elements of our indigenous flora. Wherever such garden plants appear, the nomenclature is in accordance with modern usage in the nam- ing of horticultural plants (International Code for Cultivated Plants, 1961). A few plants of Chinese origin, long established in our country, such as Mahonia japonica, Prunus japonica, Ginkgo biloba, Magnolia liliflora, Clematis florida, and some others, are also included.

The Engler and Prantl system of classification, as outlined in “Syllabus der Pflanzenfamilien,” has been adopted for the phanerogams, and Copeland’s “Genera Filicum” as the guide in the treatment of pteridophytes. The aim was to construct the analytical keys on the basis of phylogeny, but this has not al- ways been practical or possible. Purely artificial keys often have been constructed for the convenience of the user. The diag- noses of the taxa and the keys are based almost wholly on avail- able herbarium specimens.

The geographical areas covered in this flora include all of present-day Japan, excluding the Tokara Islands. The Japanese archipelago is divided into eight segments: Hokkaido (includ- ing Rishiri and Rebun islands), northern Tohoku, Kanto, central, Kinki, and western Chugoku districts of Honshu, Shikoku, and Kyushu, including the adjacent islands of Tane- gashima and Yakushima as the southern boundary.

I am deeply grateful to the late Dr. G. Koidzumi, my men- tor, for his kind instructions over a long time and to many others for their many valuable suggestions. Dr. Y. Satake, S. Okuyama, and K. Hisauchi have rendered kind assistance to the author in various ways ever since he became a staff member of the National Science Museum. Dr. T. Koyama helped in preparing the drawings, reading proof, and making indexes, as well as in various other ways. In the preparation of accounts of complex plant groups various monographic studies by spe- cialists were very helpful. To all authors of these works the writer is greatly obligated.

I wish to mention that the original Japanese edition of this work was partially sponsored by a Publications Subsidy of the Ministry of Education, for which support I am deeply grateful.


Japan supports a very rich flora in proportion to its size, a circumstance of historical importance in relation to Japan’s early closer relationship with mainland Asia and to its subse- quent development as an insular province with highly distinc- tive geographical characteristics. Historically, the Japanese home islands were a part of the continental landmass of Asia, at least down to the Quaternary Period. For this reason, our flora is most closely related to the Chinese flora, especially to plants of the mountains of China, where many species exist as relicts or as remnants of the much older Tertiary floras. That Japan was not greatly affected by Pleistocene glaciation is a factor which favored the preservation of older floras that might otherwise have vanished. Moreover, the approximately 850- mile length of the land area of Japan, extending over nearly 15 degrees of latitude from about 30° to 45° N. from the sub- tropical belt of the southern areas to the alpine summits of numerous mountain peaks——together with a complex moun- tain system that covers nearly 70 percent of the total land mass, are factors that determine the component elements of the flora.

The close proximity of the sea produces an insular climate over much of the country. The warm Japan Current or Black Stream (Kuroshio), as it flows from southwest to northeast along the Pacific side of the archipelago, influences all southern and southeastern areas, giving them a relatively high precipita- tion and little or no frost in areas near the coast. In these south- ern areas are found many plants which occur principally in areas farther south. In the north, the cool Kurile (Oyashio) Current has a pronounced cooling effect on the climate of northern Honshu. Likewise, in our northern areas and on the


higher mountains occur many boreal species extending into this area from more northerly latitudes.


This area embraces the coastal areas of southern Honshu, Shikoku, and the Pacific side of Kyushu, with a warm-temper- ate to subtropical climate influenced by the warm Japan Cur- rent (Kuroshio) from the southwest Pacific Ocean. This area is dominated largely by evergreen woody species, especially broad-leaved angiosperms. The heavy well-distributed precipi- tation of usually more than 60 inches per annum in this region results in a lush vegetation containing many plants with more southern affinities. Some common plants characteristic of this warm-temperate region are:


Camellia japonica Cinnamomum spp.

Cleyera japonica Daphniphyllum macropodum

Itea japonica Machilus spp. Myrica rubra Prunus spinulosa

Distylium racemosum Elaeocarpus japonicus Elaeocarpus sylvestris Eurya japonica

Cryptomeria japonica Pinus densiflora

Prunus zippeliana Quercus spp.

Symplocos spp. Trochodendron aralioides


Podocarpus macrophyllus Podocarpus nagi

(in the secondary forest belt)


Puants oF Rocky Piaces 1n MounTAINS

Calamagrostis hakonensis Carex spp.

Potentilla spp. Rhododendron spp.


The pioneer herbaceous plants which invade cut-over lands consist chiefly of Miscanthus sinensis, M. floridulus, Imperata, Themeda, Smilax china, Lespedeza, Rubus, and Rhododen- dron. The commonest pioneer woody species in many areas are Pinus densiflora, Mallotus japonicus, Clethra barbinervis, Calli- carpa japonica, and deciduous species of Symplocos. In the final stages of forest succession, evergreen species of Quercus and Cinnamomum reappear as climax dominants.

CoasraL DuNEs Arundo donax Calystegia soldanella Canavalia lineata Cnidium japonicum Ischaemum aristatum

Limonium tetragonum Messerschmidia sibirica Wedelia prostrata Zoysia macrostachys


Pittosporum tobira Quercus phillyracoides Rosa wichuraiana Ternstroemia gymnanthera Vitex rotundifolia

Euonymus japonicus

Eurya emarginata

Hibiscus hamabo

Juniperus chinensis var. procumbens

Litsea japonica


Actinidia rufa Hedera rhombea Hosiea japonica Kadsura japonica

Clethra barbinervis Euscaphis japonica Idesia polycarpa Mallotus japonicus Prunus jamasakura Prunus lannesiana

Piper kadsura Trachelospermum asiaticum Uncaria rhynchophylla

Decipuous TREES

Ardisia sieboldit Livistona chinensis Caesalpinia nuga Melastoma candidum Cassytha filiformis Messerschmidia argentea Cycas revoluta Microstegium ciliatum Entada phaseoloides Myoporum bontioides

Ficus microcarpa Glochidion hongkongense Ipomoea pes-caprae

Osheckia chinensis Schefflera octophylla Spinifex littoreus

Rhus javanica

Rhus succedanea

Rhus trichocarpa

Styrax japonica Zanthoxylum ailanthoides


Alocasia spp. Ardisia crenata Ardisia seboldii Arundinaria

(in forest understory) Arundo donax Broussonetia kaempferi Broussonetia kazinoki

Euryale ferox Nelumbo nucifera Nuphar japonicum

Epilobium pyrricholophum Eriocaulon spp.

Lycopus lucidus Miscanthus sacchariflorus Phragmites spp.

Debregeasia edulis Dicliptera japonica Fatsia japonica Nandina domestica Pseudopyxts sp. Rhododendron spp. Rubus trifidus Villebrunea frutescens


Nymphaea tetragona Potamogeton spp.

MarsH PLANts

Polygonum spp. Rhynchospora spp.

Typha spp. Zizania latifolia

Kandelia candel Tree-ferns

On rocks in fast-running streams in the low mountains of southern Kyushu and Yakushima are found Cladopus and Hydrobryum, both of the Podostemaceae. These are quite re- markable members of the Japanese flora, since these genera are primarily tropical with a distribution centering in India and Malaysia.

The Laurisylvae or broad-leaved evergreen forest extends northward along both the Pacific side and the Japan Sea coast of Honshu to about 38° N. latitude, where the deciduous forest species become the dominant element of the woody vegetation. Deciduous forest species, such as Quercus acutissima, O. serrata, Castanea crenata, Acer spp., Carpinus laxiflora, C. tschonosku, Alnus japonica, and A. sieboldiana, are mixed with evergreen species, Evergreen trees native in the vicinity of Tokyo are represented only by a few species of evergreen Quercus, Casta- nopsis, Machilus, and a few others.

Areas of continental eastern Asia that correspond most closely with the warm-temperate parts of Japan are the low- land and hilly areas from southern Korea to the Yangtze Val- ley and the mountainous regions of Chekiang, Fukien, Hunan, Szechuan, Kwangsi, Kweichow, and Yunnan, and from For- mosa to the western part of Sikang to the highlands of the Himalayas, Burma, and Indochina.

Significant genera found in both China and in Japan include Trochodendron, Loropetalum, Chikusichloa, Cryptomeria, Elli-


siophyllum, Chionographis, Nandina, Hosiaea, Skimmuia, Stauntonia, Hovenia, Liriope, Ophiopogon, Shibataea, Heteros- milax, and Phaenosperma. Genera such as Buxus, Camellia, Broussonetia, Aulacolepis are distributed even more widely over parts of southeastern Asia and India. While many of the species in the warm-temperate parts of Japan are endemic, very few of the genera are confined to this region. Alectorurus and Neofinetia are believed to be the only genera endemic of the Warm-temperate region of Japan.

In the warm-temperate region, endemism at the species level is perhaps best developed in the Fuji Volcanic Range and the Fossa Magna region. These areas, especially the Fuji Volcanic Range, as explained by Dr. F. Maekawa, were subject to a long period of volcanic activity during the Tertiary when they be- came pioneer areas for the development of new taxa. Campa- nula punctata var. microdonta, Carex hachijoensis, Rhododen- dron tsusiophyllum, and Astilbe simplicifolia are examples of endemic taxa found there.


Polygonum cuspidatum var. terminale

Prunus lannesiana var. speciosa

Rhododendron tsusiophyllum

Saxifraga fortune var. crassifolia

Calamagrostis autumnalis

Campanula punctata var. mucrodonta

Carex doenitzit var. okuboi

Carex oshimensis

Hydrangea macrophylla var.

normalis Styrax japonica var. Lilium auratum var. jippet-kawamurae platyphyllum Weigela coraeénsts var.

Meliosma hachijoensis fragrans


The temperate region begins at about 1,000-1,500 m. above sea level in Kyushu and southern Shikoku, thence gradually decreasing in altitude northeastward to the low mountains of the Kanto District. The temperate region descends to sea level at about 38° N. latitude and continues northward along the coastal areas to the southwestern part of Hokkaido, including the southern province of Tokachi. The intermediate forest zone between the warm-temperate and temperate regions are usually dominated by Quercus acutissima, O. serrata, Castanea crenata, and Pinus densiflora. In the temperate region Cryptomeria japonica, Chamaecyparis obtusa, and C. pisifera are widely cul- tivated, but the larger bamboos are no longer very evident. Plants common in the temperate region are:

Decipuous TREES

Fraxinus sieboldiana Hamamelis japonica Kalopanax septemlobus Magnolia obovata Prunus sargentit Prunus verecunda Quercus mongolica Sorbus alntfoha Sorbus commixta Sorbus japonica Styrax shiraiana Tilia japonica Ulmus laciniata Viburnum furcatum

Acer japonicum

Acer mono

Acer palmatum

Aesculus turbinata

Alnus hirsuta

Betula grossa

Betula maximowicziana

Betula schmidti

Carpinus cordata

Carpinus japonica

Fagus crenata

Fagus japonica

Fraxinus mandschurica var. japonica


Abies firma

Abies homolepis Larix leptolepis Pinus koraiensis Pinus pentaphylla Pseudotsuga japonica

Sciadopitys verticillata Taxus cuspidata Thuja standishit Thujopsis dolabrata Tsuga diversifolia Tsuga sieboldu


Aucuba japonica Daphniphyllum humile Euonymus fortunei

Ilex leucoclada Ilex sugeroki Skimmia japonica

Decipuous SHRUBS

Hydrangea macrophylla var. acuminata

Ilex serrata

Kerria japonica

Lespedeza spp.

Lonicera spp.

Sorbus gracilis Spiraea japonica Tripetaleia paniculata Vaccinium spp.

Decipuous Lianas

Actinidia polygama Akebia quinata Akebia trifoliata Hydrangea petiolaris

Rhus ambigua Schizophragma hydrangeotdes Tripterygium regelit

Vitis coignetiae


Cacalia spp.

Chrysosplenium spp.

Circaea spp.

Cirsium spp.

Gentiana scabra var. buergert

Melampyrum laxum Plectranthus trichocarpus Saussurea spp.

Trillium spp.

Viola spp.


Anemonopsis (Ranunculaceae) Deinanthe (Saxifragaceae) Glaucidium (Ranunculaceae) Hakonechloa (Gramineae) Kirengeshoma (Saxifragaceae)

Peltoboykinia (Saxifragaceae) Ranzania (Berberidaceae) Sciadopitys (Coniferae) Thujopsis (Coniferae) Tripetaleia (Ericaceae)


Calystegia soldanella Carex hobomugi Carex pumila

Imperata cylindrica Ixeris repens Zoysia macrostachya


Arabis stelleri Lathyrus maritimus Linaria japonica

Messerschmidia sibirica Rosa rugosa Thermopsis lupinoides

PLants CoMMoNLY Founp IN Rocky PLaces ALONG THE Coast

Chrysanthemum yezoense Lystmachia mauritiana

Sedum kamtschaticum


Pinus thunbergit

Quercus dentata

Mars PLanTs oF CoasTaL AREAS

Aster tripolium Carex rugulosa Carex scabrifolia

Fimbristylis subbispicata Triglochin maritimum

Aguatic PLants

Aldrovanda vesiculosa Brasenia purpurea Myriophyllum spicatum Najas marina

Najas minor

Nuphar subintegerrimum

Potamogeton spp. Ranunculus nipponicus Sparganium spp. Utricularia spp. Vallisneria asiatica



Caltha palustris Carex dickinsit Carex dispalata Cyperus glomeratus Eleocharis spp. Eriocaulon spp. Lycopus untflorus Rhynchospora spp.

Scirpus juncoides

Scirpus lacustris var. creber Scirpus mitsukurianus Scirpus preslit

Scirpus triqueter

Scirpus wichurae Sparganium stoloniferum Typha latifolia


Adenophora palustris Astragalus adsurgens Campanula glomerata Carex cinerascens Carex leiorhyncha Carex lithophila Carex meyeriana Carex neurocarpa

Carex onoei

Lilium callosum Polygonatum inflatum Senecio flammeus Trigonotis nakaun Triosteum sinuatum Viburnum carlesit

The temperate flora of Japan shows close relationship to that of certain areas of mainland eastern Asia, especially with the mountainous areas of southern Korea and the lowlands of cen- tral Korea and the Huan River valley, also with the mountain- ous regions of central China and the high mountains of the Himalaya and Malaysia.


The coastal areas of the Japan Sea side of Honshu, centering around Hokuriku from San’in District as far north as the west coast of Ugo Province, contrast rather sharply in climate with areas of the Pacific Coast at the same latitude. The winters on the Japan Sea side are considerably more humid than those on the Pacific side with much more snow in the mountains and along coastal areas. Coniferous forests of Abies, Picea, and Tsuga are charasteristic of the Pacific side of the country.


Actinidia Euptelea Aimshaea Helwingia Akebia Hosta Aucuba Hovenia Cercidiphyllum Peracarpa Cryptomeria Tricyrtis Dammnacanthus Weigela Deutzia


Agrostis hideot

Alnus fauriei

Berchemia longeracemosa Calamagrostis fauriet Calamagrostis gigas Camellia rusticana

Carex aphyllopus Chrysosplenium fauriet Corydalis capillipes

Hamamelis japonica vat. obtusata

Tlex leucoclada

Tris gracilipes

Pedicularis nipponica

Poa fauriei

Ranzania japonica

Tripterygium regelit

Viola fauricana

Adenophora Hedera Adonis Ilex Bothriospermum Pseudostellaria Kengia Syringa Eranthis Thelygonum Forsythia

The relationship of the flora of Japan to that of North Amer- ica, especially eastern North America, was first elucidated by Asa Gray in his now classic paper published in the Memoirs of the American Academy of Arts and Sciences (see footnote p. ix). Gray first elcuidated the close affinities that exist be- tween the two areas. This floristic relationship is now explained on a historical basis of a former land-bridge connection be- tween Asia and North America across the Bering Sea in pre- glacial times. Most of the American representatives of genera common to both areas are considered by most authors to be distinct from those in Japan, but in some instances the Ameri- can and Japanese taxa may be distinguished only with diff- culty.


Apios Meehania Boykinia Menispermum Buckleya Menziesia Caulophyllum Muhlenbergia Clethra Osmorhiza Croomia Pachysandra Cryptotaenia Phryma Diarrhena Shortia Diphylleia Stewartia Epigaea Tipularia Hamamelis Torreya

Ttea Trautvetteria Leucothoé Tsuga Lespedeza Wisteria Magnolia Zizania

Epimedium sempervirens

Several gigantic herbaceous plants are found in the wet coastal areas of the Japan Sea side, the most common being Petasites japonicus var. giganteus, Polygonum sachalinense, Cacalia hastata var. orientalis, Urtica platyphylla, Angelica matsumurae, A. edulis, A. ursina, and Filipendula kamtscha- tica.

In the mountains near the Japan Sea coast where winter snows are deep, the alpine zone descends to a relatively low elevation and the development of moors is a prominent aspect of the high mountainous districts of this region. Among the common species in wet alpine meadows are Fauria crista-gallz, Tofieldia japonica, Narthecium asiaticum, Phyllodoce aleutica, Boykinia lycoctontfolia, Scirpus caespitosus, Scirpus hondoensis, Juncus beringensis, Geum pentapetalum, Plantago hakusanen- sis, and Primula cuneifolia var. hakusanensis. This mountain flora appears to be most closely related to that of more northern areas in Kamchatka and Alaska where snowfall is heavy and the climate is moist.

In the Hokuriku region of the Japanese alps where heavy winter snow weighs down all shrubby vegetation, most of the understory shrubs are nearly prostrate or at least decumbent. The occurrence of broad-leaved evergreen shrubs in this re- gion, such as Ilex leucoclada, Camellia rusticana, Daphniphyl- lum humile, Cephalotaxus harringtonia var. nana, Ilex crenata var. paludosa, is possible because of a protective covering of deep snow in winter. Also found here are Chikusichloa aqua- tica and Diplaziopsis cavaleriana, both represented more widely in the warm-temperate areas of western Japan.


The boreal region of Japan is characterized by a coniferous forest belt composed of Abies mariesii, A. homolepis, A. mayri-


ana, A. veitchit, Picea jezoensis, Larix kaempferi, Tsuga d1- versifolia, and Taxus cuspidata, which occurs at altitudes up to 2,000 m, in the western parts of Honshu and Shikoku. In the central district of Honshu this zone occurs from 1,500 to 2,000 m, altitude. In the northern districts of Honshu the coniferous belt is found from 1,000 to 1,500 m. altitude and to near sea level in the eastern and northern parts of Hokkaido. Common plants of this boreal region are:

Decipuous TREES

Betula playtyphylla Prunus ssiori

Sorbus commixta Sorbus matsumurana

Acer tschonoskiu Alnus matsumurae Alnus maximowiczit (upper zone) Betula ermanu

Decripuous SHRUBS Salix rein Vaccinium yatabet

Euonymus tricarpus Oplopanax Japonicus


Rhododendron brachycarpum Rhododendron degronianum

Tlex rugosa Ilex sugerokt


Matanthemum dilatatum Microstylis monophyllos Platanthera ophrydioides Trientalis europaea

Circaea alpina var. caulescens Cornus canadensis

Epilobium spp.

Glyceria alnasteretum


Actinidia kolomikta Rhus ambigua


Arabis stelleri var. Artemisia stelleriana Carex gmeliniz Elymus mollis Glehnia littoralis Honkenya peploides Lathyrus maritimus

Linaria japonica

Matricaria matricarioides Matricaria tetragonosperma Mertensia asiatica

Rosa rugosa

Scutellaria strigillosa


Chrysanthemum arcticum Potentilla megalantha

Trifolium lupinaster

PLANTs OF LirroraL Swamps IN CoasTaL AREAS

Carex lyngbyet Carex mackenziei Glaux maritima Salicornia europaea

Scirpus planiculmis Triglochin maritimum Triglochin palustre


Nuphar pumilum Polygonum amphibium Potamogeton heterophyllus

Scirpus tabernaemontani Sparganium gramineum


Andromeda spp. Ledum spp.

Carex curta Narthecium asiaticum Carex limosa Rhychospora alba Carex middendor ffii Scheuchzeria

Drosera angelica Tofteldia japonica

Drosera rotundifolia Eriophorum spp.

Vaccinium oxycoccus


Alnus hirsuta Calamagrostis langsdor ffi Epilobium angustifolium Phragmites communis

Polygonum sachalinense Salix spp. Scirpus wichurae

The genera found in the boreal region mostly are those with a wide circumboreal distribution. Only Pteridophyllum, Dac- tylostalix, and Tripetaleia are endemic of this floristic province.

Coniferous forests are widely scattered in the high moun- tains of the Japan Sea side, consisting, when they do occur, mainly of Thuja standishii and Larix leptolepis. Deciduous woody species predominate in the vegetation of this region, include Acer tschonosku, Alnus maximowiczu, Betula ermanit, Hamamelis japonica var., Magnolia salicifolia, and Sorbus matsumurana.

In lowlands, especially near the seacoast of eastern Hok- kaido centering in the provinces of Nemuro and Tokachi, fogs in summer are of frequent occurrence as a result of the cold Kurile Current which flows southwestward along the south coast. Moors in this area are well developed. Carex subspatha- cea and C. mackenziez occur in the littoral swamps, the only areas where these plants appear in Japan. In the coastal area are Saxifraga bracteata, Potentilla megalantha, Cochlearia oblongt- folia, Rhododendron parvifolium, and Fritillaria camtschatcen- sis, these having reached our area from farther north.


Extensive arctic-alpine areas are not represented in Japan, although treeless tundralike areas of limited extent occur on several mountain peaks scattered over various parts of the country. In the central district of Honshu, the alpine zone occurs at elevations of about 2,500 m. In the northern district of Honshu it begins at about 2,000 m. and at 1,500 m. in Hok- kaido. Characteristically, the alpine zone is represented by a shrubby pine, Pinus pumila, except on the more recent vol- canoes, such as Mount Fuji and Mount Asama. Immediately below the Pinus pumila zone deciduous shrubs are prominently represented, mainly Alnus maximowiczu, Betula ermanit, Pru- nus nipponica, Vaccinium uliginosum, V. axillare, Sorbus sambucifolia, and S. matsumurana, mixed with many high- altitude herbaceous plants. In the alpine zone, the plants con- sist mainly of Ericaceae, Primulaceae, Caryophyllaceae, Gen- tiamaceae, Scrophulariaceae, Ranunculaceae, Rosaceae, and Cruciferae. The genera of the alpine zone mostly are those widely distributed throughout the northern parts of the North- ern Hemisphere. The only endemic genus of the alpine area of Japan is Japonolirion, found on serpentine rocks. Most of the species of alpine plants found in Japan occur also in eastern Si- beria, Alaska, the Aleutians, and Kamchatka, or represent widely distributed circumpolar species. Very little relationship is shown between the alpine plants of Japan and those of the Sino-Himalayan area, although Polystichum lachenense (Fil- ices) and the genus Androcorys (Orchidaceae) occur in both areas.

Recent vulcanism in Mount Fuji, Mount Asama, Mount Iwate, Mount Chokai and in some other areas may be responsi- ble for the occurrence of alpine species at lower elevations than on nonvolcanic mountain peaks found elsewhere.

Local endemism on Mount Hayachine, Mount Shibutsu, and Mount Apoi is associated with serpentine rocks found on these mountain peaks. The incidence of alpine plants is relatively


high on Mount Apoi as a result of a lowered summer tem- perature brought on by heavy fog during the growing months of summer. The flora of Rebun Island, adjacent to Hokkaido, is known for the occurrence of floristic elements from Sakhalin as a result of a lowered summer temperature brought on by the cold current that flows southward through the Mamiya Channel.


When Linnaeus wrote the first edition of his “Species Plan- tarum” in 1753, he knew only a few of the plants of Japan, all taken from the “Amoenitatum Exoticarum” (1712) of Engelbert Kaempfer (1651-1716). Kaempfer was a German naturalist who lived in Japan from 1690 to 1692 as a medical officer of the Dutch East India Company. The plants listed by Kaempfer were: Chenopodium scoparia, Rhus vernix, Laurus camphora, Thea sinensis, Uvaria japonica, Camellia japonica, Morus papyrifera, Xanthium strumarium, Ficus pumila, Smilax china, Taxus nucifera, Epidendrum moniliforme, Azalea in- dica, etc., all well known among the indigenous plants of Japan.

In volume I of Linnaeus’s “Mantissa Plantarum” (1767), Sophora japonica, Prenanthes japonica, and Tussilago japonica were described on the basis of actual specimens collected in 1759 by Christiaan Kleynhoff, a Hollander of German birth. The next year Kleynhoff’s collection was reported upon by N. L. Burman (1734-1793), also of Holland, in his “Flora Indica” (1768). In Burman’s work Azalea rosmarinifolia, Basella japonica, Arnica tussilaginea, and Ficus pyrtfolia are described from Japan as new taxa based upon Kleynhoff’s original speci- mens.

C. P. Thunberg (1743-1828), a Swedish naturalist, phys- ician, and disciple of Linnaeus, came to Japan in August of 1775 at the age of 32 years, as a medical officer of the Dutch East India Company. Thunberg traveled from Nagasaki to Yedo (Tokyo) and back before his return home via Java in December of 1776. Thunberg’s Japanese collections amounted to approximately 1,000 species. The best of his collection was from Hakone. The major work of Thunberg culminated in his now classic work “Flora Japonica,” published in 1784, the cornerstone of taxonomic botany in Japan. Thunberg pub- lished separately on parts of his Japanese collections in “Kaempferus Illustratus,” 1-2 (1780, 1783); “Nova Genera Plantarum,” 1 and 3 (1781, 1783), and several other works. Several novelties from his collection were published in “Sup- plementum Plantarum Systematis Vegetabilium” (1781) by the son of Linnaeus and in part 2, volumes 8-14, of the “Natuurlyke Historie” (1773-83) of Martinus Houttuyn. Nearly all of Thunberg’s collections are now preserved in the University of Uppsala in Sweden.

Through the Dutch East India Company, established in Nagasaki in 1609, Japanese plants found their way to Europe via Dejima Island, the only Japanese port opened to foreigners at that time. Only ships of Dutch nationality were permitted ‘entry until restrictions were removed in 1859. Floristic studies on the Japanese flora during this period, although of a rela- tively limited scope, were carried on under Dutch sponsorship. Botanical collecting by the Dutch was greatly accelerated after the beginning of the 19th century by the opening of a botanical garden at Buitenzorg (now Bogor) in Java and by the ex-

ploits of Siebold and others. Japanese plants from various col- lectors were studied by K. L. von Blume (1796-1862) at Bui- tenzorg. We find that publication on some of Siebold’s early collections began to appear in volume 2 of Blume’s “Bijdran- gen tot de Flora van Nederlandsch Indie” (1825-26).

P. F. von Siebold (1796-1866), of German birth, came to Japan in 1823 when he was 27 years of age as a medical officer of the Dutch East India Company. He remained in Japan until 1829. During his residence of six years he collected assiduously at Nagasaki and vicinity, and in 1826 he traveled to Yedo (Tokyo) and back. Siebold was assisted at various times by the able Japanese naturalists Keiske Ito (1803-1901), Yoan Uda- gawa (1798-1846), and Hobun Mizutani (1779-1833). Upon his return to Europe in 1830, Siebold lived at Leiden and conr- tinued to receive plants from Japan sent through his Japanese acquaintances, from H. Buerger who had earlier collected plants with Siebold, and from Jacques Pierot (1812-41) who visited Japan in 1840. Plants also came from Otto Gottlieb Johan Mohnike (1814-87). For a time Siebold operated the commercial nursery of Siebold & Co. at Leiden and sold many Japanese plants widely