Contributions to the Anatomy of Mesozoic Conifers No. I. Jurassic Coniferous Woods from Yorkshire1

Abstract

DURING been investigated the last few anatomically, years, a large and number found to of throw Cretaceous considerable woods have light e investigated anatomically, and f und to throw considerable light on the inter-relationships of the various families of Conifers. Structurally preserved material from the Jurassic is comparatively rarer and less known, but seems to be of even greater value than the Cretaceous from this standpoint. Especially interesting are those specimens described by Professor Seward from Yorkshire, England (1), by Gothan from King Karl's Land (2) and the island of Spitzbergen (3), and by Lignier from Normandy (4). The woods to be described in this article are all from the Jurassic of Yorkshire. They are in two conditions of preservation petrified and lignitic. With a few exceptions, the petrified material was sent by Mr. James Lomax to Professor Jeffrey, to whom the writer is indebted for an opportunity to study it. All the lignite, on the other hand, and a small number of petrified specimens, were obtained by the writer from various localities on the Yorkshire coast. All the sections from Mr. Lomax, and representative ones of the lignitic material, are now at the University Museum, Harvard College, Cambridge, Massachusetts. Before entering on the descriptive part, it will be apposite to consider briefly those features which have been found to be of greatest significance in diagnosing woods, especially in differentiating between the two great groups of Conifers Araucarian and nonAraucarian, or Abietineous. The earliest classification, that of Kraus (5), was based entirely on the character of the radial pitting of the tracheides the pits being alternating and compressed in the Araucarineae, and opposite and separated in the Abietineae and other tribes. This is the criterion used by both Seward and Lignier. Jeffrey (6), however, has shown that in the Cretaceous there were woods which combined the Araucarian type of pitting with that characteristic of