2007年6月 尾瀬ヶ原 |
また,東京都立大学牧野標本館所蔵のシーボルトコレクション*には,2点のサンカヨウの腊葉標本が保存されている(左図).いずれにも果序の墨絵があるが,一つには「ヤマボタン 下野湯本産」と記載があり(MAKS0115),もう一つは水谷助六作成の標本と考えられている(MAKS0114).しかし,シーボルトはサンカヨウをアメリカサンカヨウ (D. cymosa Mich.) と同一種と考えていたようで,彼の著作には,サンカヨウに関する記述はない.
*ロシア,レニングラード市(現サンクト・ペテルブルグ市)のコマロフ植物研究所から交換標本として送られてきた“シーボルトコレクション”の大部分はシーボルトが滞日した1823-1829年および1859-1862年に収集した植物標本である.シーボルトがミュンヘンで亡くなった後に,ロシア人の植物分類学者マキシモヴィッチ(Carl Johann Maximowicz, 1827-1891)が未亡人より購入したもので,約100年ぶりに日本に帰ってきた.
Flora Boreali-Americana (Michaux), 1: tt. 19-20 |
日本産のサンカヨウを米国産のそれと同一とする誤りは長く続いた.
“Bathing Scene in Japan “ |
その腊葉を研究したのが,ハーバード大学のエイサ・グレイ教授であったが,その標本の中にJ.スモールが,北海道の宗谷岬付近で採集したサンカヨウがあった.
グレイ教授はこのサンカヨウを,北米に自生しているアメリカサンカヨウと同一種と考え,函館で採取されたメギ科のルイヨウボタン(Caulophyllum robustum)(これも北米原産の Caulophyllum thalictroides とした)と共に,彼が発見した「東アジア・北米隔離分布」説の有力な証拠とした( Mem. Amer. Acad. Arts Sci. (Boston) n. s. 6 379, 1859).
IX. Diagnostic Characters of New Species of Phaenogamous Plants, collected in Japan by Charles Wright, Botanist of the U. S. North Pacific Exploring Expedition. (Published by Request of Captain John Rodgers, Commander of the Expedition.) With Observations upon the Relations of the Japanese Flora to that of North America, and of other Parts of the Northern Temperate Zone.
By ASA GRAY, M. D. (Read December 14, 1858, and January 11, 1859.)
Berberidacae . We have both the true Berberis vulgaris and B. Thunbergii, DC, thelatter very near B. Cretica, and accordingly hardly distinguishable from our own Alleghanian B. Canadensis. The Japan Mahonia, a link between the Western American and Himalayan species, I have not seen. Nor was a single Epimedium collected, although Japan is apparently the focus of the genus. But perhaps the most interesting and most unexpected discovery of the expedition is that of two strictly Eastern North American species of this order, - each the sole representative of their genus, - viz. Caulophyllum thalictroides, and Diphylleia cymosa, of Michaux. The former was gathered near Hakodadi, and also on the northern end of Nippon, - out of blossom, indeed, but with the ovaries just bursting, and the later specimens with the peculiar seed well formed. The latter, J. Small found at Cape Soya, the northeastern extremity of Japan, in fruit only. So that flowers are wanted to confirm the identity, of which, however, I have scarce a doubt.
CBM Diphylleia cymosa (1814) |
Supposing these two plants to be satisfactorily identified as to species, are we to regard them as the descendants of a common stock, though now separated by one hundred and forty degrees of longitude ? Or are we to suppose them independently originated in two such widely distant regions? The collocation of a larger body of such facts may lead to a satisfactory answer to these questions.
(中略)
The geographical range of this species, as now extended, is instructive. This, and the numerous similar instances already mentioned, or to be mentioned, are particularly recommended to the consideration of those (such as De Candolle the younger) who,although convinced that species in general have had a single, local origin, are yet con-strained to adopt the hypothesis of a double origin in the special case of certain species known to occur only in two widely dissevered regions ; - e. g. Phryma leptostachia in Nepaul, as well as in North America east of the Mississippi ; or our own Diphylleia and Caulophyllum, occurring only here and in Japan. The number of instances, 1. of species strictly divided between Eastern North America and some part of Northern Asia ; and 2. of those which are known to occur at one, two, or several intermediate stations, - is already so increased, that they can no longer be regarded as exceptional or casual, but must evidently receive a common explanation. And what that explanation is begins to be clear.
グレイ教授の見た標本はいずれも花のない個体であったので,日本産品を米国産品と分別できなかったのであろうが,彼の提唱した「東アジア・北米隔離分布」説を損なうものではない.この説はそのほか多くの植物でも確認され,地質学的な古代に,北米大陸とユーラシア大陸が北部で陸続きであった事の強力な生物学的証拠と認められている.
後にサンカヨウは F. シュミット(Schmidt, Friedrich (Karl) (Fedor Bogdanovich), 1832-1908) によって,米国産とは別種であることが確認され,グレイ教授に献呈され,D. grayi と命名された (Reis. Amur-Land., Bot. 109. 1868,左 図).
また,主に中国北部に分布する同属の山荷葉は Hui Lin Li (1911-2002) によって D. sinensis の学名がつけられた(J. Arnold Arbor. xxviii. 443. 1947).
現在確認されているサンカヨウ属の植物はこの三種のみであり,「東アジア・北米隔離分布」説にとって重要な植物である.
サンカヨウ(1/3) 草木図説・中国の山荷葉(D. sinensis,Astilboides tabularis ),薬効
サンカヨウ(3/3) 鬼臼 新修本草・本草和名・延喜式・本草綱目・和漢三才図会・本草綱目啓蒙・梅園草木花譜,増補古方薬品考
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