FURTHER OBSERVATIONS ON PALEOROSA-SIMILKAMEENENSIS (ROSACEAE) FROM THE MIDDLE EOCENE PRINCETON CHERT OF BRITISH-COLUMBIA, CANADA

Reinvestigation of the holotype and paratypes, as well as four new flo wers of Paleorosa similkameenensis Basinger, have provided additional morphological and anatomical features to further characterize this ear ly rosaceous flower. Noted features include the presence of a follicul ar fruit composed, at least in part, of thick-walled cells, seeds with possible remnants of embryonic tissue and hypostase, and pollen morph ology and ultrastructure. The fruit is a follicle enclosed by a non-fl eshy floral cup. Based on this fruit type Paleorosa is assigned to the Spiraeoideae. Although fruit morphology strongly supports inclusion o f Paleorosa in Spiraeoideae, floral structure such as short, post-chal azal branching of the raphe and pollen morphology show similarities to Maloideae, particularly the genus Pyracantha Roemer. Paleorosa pollen is prolate and tricolporate with indistinct pores. The exine is stria te, semi-tectate/columellate, and the sexine is thicker than the nexin e. The intermediate characters of Paleorosa add strength to the hypoth esis that Spiraeoideae may be ancestral to Maloideae. In addition, the se intermediate characters provide further evidence for an important r adiation of Rosaceae during the Eocene. This fossil material provides the opportunity to understand the pollen structure of the Rosaceae fro m the Eocene.