1941 Volume 1941 Issue 21 Pages 40-42
More than 40 species (of which six are living) of Platanus are known in the world, the oldest known being the Cretaceous. They may tentatively be divided into four groups in respect to the foliar characters:(1)Racernosa group, leaf deeply lobate, (2) Aceroides-occidentalis-orientalis group, leaf shallowly lobate, (3) Guillelmae group, leaf not lobate or obsoletely lobate, and (4) Basilobata group, leaf peltate. Of these groups, the foliar characters between (2) and (3) appear to merge gradually from one to another in many cases:
Among the Tertiary plants of Hokkaido and Karahuto the present authors discriminated six different types as follows:
P. aceroids GOEPP.
Isikarian Stage (Palaeogene).
Hokkaido: Woodwardia Sandstone of Central Hokkaido;
Uryu coal-bearing beds of the Uryu coal-field.
Karahuto: Naibuti coal-bearing beds.
Urahoroian Stage (Oligocene-Miocene).
Hokkaido: Syakubetu coal-bearing beds of eastern Hokkaido.
P. Guillelmae GOEPP.
Hokkaidô: Woodwardia Sandstone.
Karahutô: Naibuti coal-bearing beds.
Syakubetu coal-bearing beds in eastern Hokkaidô.
Kawabataian Stage (Miocene).
Hokkaidô: Kayanuma coal-bearing beds of the Kunnui Series in southwestern Hokkaidô (as cfr. P. Guillelmae).
Cfr. P. aceroides latifolia KNOWLT. Isikarian Stage.
Woodwardia Sandstone of Central Hokkaido.
P. Mabutii sp. nov.
Urahoroian Stage (Syakubetu coal-bearing beds). P. sachalinensis ENDO.
Isikarian Stage (Naibuti coal-bearing beds of Karahuto). P. Heeri LESQ.
Cretaceous (near Due coal mine, Russian Karahuto).
P. aceroides and P. Guillelmae are common and occur in association in most cases. Cfr. P. Guillelmae occurs from the Neogene beds of the Kayanuma coal mine, and this is the youngest record of fossil Platanus in the Asiatic continent (the authors recently recognized another Neogene Platanus from the Engelhardtia-bed of Tyôsen). P. Mabutii and P. sachalinensis are characterised by having peltate blade. Cfr. P. aceroides latifolia resembles the original specimen but is somewhat imperfect to admit precise comparison. P. Heeri has been recorded only from the Russian Karahuto but not known from Japan.
In Hokkaidô and Karahuto the development of Platanus began from the Cretaceous and it flourished most in the Palaeogene. It may be certain that it existed also in the early Neogene, but possibly disappeared since that time from these islands.
The details may be printed in the Journal of Faculty of Science, Hokkaidô Imperial University