Wheeler, E.A. and Manchester, S.R. Woods of the Eocene nut beds flora, Clarno Formation, Oregon, USA. IAWA Journal, Supplement 3

IAWA (International Asso ciation of Wood Anato mists) publishes a high quality journal in four parts, comprising about 500 pages a year. Every so often they publish supplements that are much longer and more comprehensive than traditional scientific papers. The first two were Bibliography of systematic wood anatomy of dicotyledons (265 pages) by Mary Gregory (1994) and Wood anatomy of Sapindaceae (214 pages) by Rene Klaasen (1999). This third supplement is on a fossil flora which has many well‐preserved woods that have now been studied in detail. The only minor criticism I have is that the title of this supplement is as shown above on the front cover, but the inner pages are all more specific: ‘Woods of the Middle Eocene . . .’. The cover shows a beautifully pre served transverse section of Alangium oregonensis, and whets the appetite to dig deeper. This is a very thorough and detailed account of the fossil woods found in the Middle Eocene Clarno formation, which was deposited around 44 million years ago. The authors have examined 600 silicified wood samples, and assigned them to 66 genera and 76 species. This comprises the most diverse fossil wood assemblage from a single locality, and is of great scientific value, because there are also many co‐occurring fruits and seeds, which have been assigned to 145 genera and 173 species, and leaf fossils also occur. These fossils are from a time when the warm equable climate of the early Eocene was changing to the cooler more seasonal climates that we know today. Many of the woods have indistinct growth rings, suggesting that the climate was only weakly seasonal, and probably warm temperate to subtropical. Modern tropical lowland trees often have a few wide vessels, but none of the Clarno woods show this. Twenty‐two per cent of the woods have scalariform perforation plates, and 29 % are semi‐ring porous. All the wood genera described that still exist now occur in eastern Asia, 50 % are shared with eastern North America and 50 % with Malesia. Only 5 % of the woods were identified as lianas, whereas 43 % of the fruits and seeds have been. Discrepancies between the fossil woods and seeds and fruits are discussed thoroughly, with suggestions on why this should be. The introductory chapters provide a wealth of information. The materials and methods section provides a good description of the locality and occurrence of the fossils, how the collections were made and where they are now kept. The woods were silicified, often abraded and jumbled, and clearly not fossilized in situ. The method of preparation for microscopy and the process of identification are described. The philosophy of how names were applied is explained. The authors have divided the woods into five groups according to their relationship to extant plants. These are (1) extant genera, where the anatomy is the same as that in a present‐day genus; (2) extinct genera, where the fossil can be identified as belonging to an existing family, but has a combination of anatomical features not occurring in today’s genera; (3) stereotype genera, which cannot be assigned to an extant genus because the same combination of features occurs in more than one genus; (3a) ordinal genera, which have features that occur in more than one family, but these families belong to the same monophyletic clade (i.e. order); and (4) form genera or xylotypes, which cannot be assigned to a family or order. The last group could include genera that still exist, but have not been examined or recognized from reference material. The bulk of this work comprises detailed descriptions and photomicrographs of the woods. Considering the age of these fossils, their preservation and the quality of the photographs is remarkable. The sections are often as good as those of modern woods. The authors have taken a cautious approach with their identifications and ordering of descriptions. These begin with dicotyledon woods identified to family (Aceraceae, Alangiaceae, Anacardiaceae, Annon aceae, Araliaceae, Betulaceae, Cercidiphyllaceae, Fagaceae, Hamamelidaceae, Juglandaceae, Lauraceae, Leguminosae, Magnoliaceae, Malvaceae, Platanaceae, Rosaceae, Sabiaceae, Sapindaceae, Ulmaceae, Vitaceae), followed by those referable to orders (Malpighiales, Sapindales, Urticales), then those with uncertain affinity, which are divided into ‘xylotypes’ (three groups). The xylotypes have been divided into woods with exclusively scalariform perforation plates (further subdivided into those with solitary vessels and wide rays over 10 cells wide, those with vessels in radial multiples and solitary with rays over 10 cells wide, and those with narrower rays), woods with both scalariform and simple perforation plates, and those with exclusively simple perforations (subdivided into vines with or without interxylary phloem, semi‐ring to ring porous woods, and diffuse porous woods). For each taxon or group account there are headings for comments. These include characters which would have been needed to aid an identification, but were absent because of poor preservation, and similarities to extant woods. This part of each account is very helpful, because it gives an insight into the process of coming to an identification, and provides a great deal of information on the anatomy of extant woods as well as the fossils. The remainder of the taxon accounts are palms and gymnosperms (Pinaceae, Taxodiaceae, Ginkgoaceae, conifers of unknown affinities). The publication of so many descriptions and good photographs, even of unidentified material, means that future researchers on Clarno woods will have most of what they need in this single volume. The authors have provided a detailed, beautifully illustrated and well‐designed book. It will be an essential reference for those working on Eocene and Tertiary floras, and is a sobering reminder to those of us who work on modern woods how difficult fossil woods are to prepare and identify. The book will be a permanent record of a fossil wood flora, and will be the standard reference for many years to come. I thoroughly recommend it to anyone interested in the evolution of flowering plants and/or wood anatomy.