XVI International Botanical Congess

Fossil woods are abundant in Cretaceous of Hokkaido, Japan. We collectedmore than 140 dicotyledon woods of Albian, Cenomanian, Turonian, Coniacianand Santonian stages. Among them, there is no homoxylous wood. We recognized 19 types of wood provided with vessels. Pores are most solitary and in multiples in some others. Perforation plates are scalariform in 13 types and simple in 4 types, while mixture in 2 types. Wood parenchyma is diffuse, diffuse-in-aggregate and vasicentric. Non-perforate tracheary elements are fiber-tracheids and vasicentric tracheids. Rays are full of variety: uniseriate rays only, several-seriate narrow rays, wide rays, and very large rays. Oldest woods (Icacinoxylon-type) was from Albian, which is the oldest dicotyledon woods in Japan. First appearance of woods provided by exclusively simple perforation plates was Cenomanian. It was clarified that wood structure was fully differentiated during early stages of late Cretaceous.