PINUS POLLEN CONES FROM THE MIDDLE EOCENE PRINCETON CHERT (ALLENBY FORMATION) OF BRITISH-COLUMBIA, CANADA

Anatomically preserved pollen cones are described from the Middle Eoce ne Princeton chert of British Columbia, Canada. Cones are ellipsoidal; range from 2.8 to 6.9 mm in length, 1.6 to 3.5 mm in diameter; and ar e often subtended by scale leaves. Cone axes contain longitudinally or iented, cortical resin canals and 14-18 vascular bundles. Microsporoph ylls are helically arranged each bearing two abaxial pollen sacs, many containing pollen grains. Grains are bisaccate and monosulcate, rangi ng from 50 to 70 mu m in length and 27 to 43 mu m in width. Proximally , the corpus is rugulate with a tectate-alveolate infrastructure. Sacc i have a well-defined endoreticulum and an external ornamentation that is psilate to scabrate. Variations in cone size, cone anatomy, and po llen morphology indicate that several developmental stages are preserv ed. The large number of cones present in the chert, especially those r epresenting short-lived ontogenetic stages, and the preservational qua lity of the cones support depositional interpretations for a rapid bur ial and preservation. These factors also indicate that the pollen cone -producing plants occupied a marginal position in proximity to the lac ustrine environment. Four species of Pinus, based on woody twigs, dwar f shoots, leaves, and ovulate cones, are presently known from the Prin ceton chert. The association of these pollen cones with Pinus similkam eenensis leaves and Pinus arncddii ovulate cones indicates possible ta xonomic affinities among these species. The Princeton chert specimens are the oldest Pinus pollen cones to be described and are the first in the genus for which fossil pollen ultrastructure has been described.