Search

Seventeen small, staminate flowers, 3.0–4.5 mm long × 1.0–1.5 mm wide, representing two developmental stages of the same type of flower have been recovered from the Middle Eocene Princeton chert locality of British Columbia. Some specimens are immature buds with overlapping perianth parts enclosing the stamens; others represent mature flowers with an open perianth. Flowers are pedicellate with a small flat receptacle bearing a perianth of at least three sepals and up to four petals. Five specimens show a three- to four-lobed rudimentary pistil surrounded by an intrastaminal nectary disk. The 10 stamens are included or barely exserted with nonconnate filaments, 1.2–2.0 mm long, attached by a slender connective to large dithecal anthers up to about 0.9 mm long that open by longitudinal slits. The anther wall is represented by a palisadelike endothecium composed of cells that are thick-walled and radially elongated relative to the long axis of the anther. Abundant in situ pollen is semitectate–columellate, tricolporate, subprolate to prolate, and prominently striated with equatorially bridged colpi. This fossil combines flower and pollen characteristics similar to those of the Sapindaceae, resembling most closely the tribe Dodonaeeae. Key words: Sapindales, Dodonaeeae, Tertiary, permineralization, flowers, pollen.

One small monocotyledon petiole, 1.8 × 1.5 mm wide, has been recovered from the Princeton chert in the Middle Eocene Allenby Formation, British Columbia. The petiole, rectangular in transverse outline, shows approximately 36 circular to oval-shaped vascular bundles within aerenchymatous ground tissue that includes tannin cells. The epidermis is underlain by a discontinuous hypodermis of thick-walled, pitted cells. Vascular bundles are in five series: (I) a median U-shaped arc of 11 – 13 bundles; (II) an abaxial arc of 6 bundles located below the main arc; (III) two short abaxial arcs of 3 bundles each; (IV) 2 bundles just below the abaxial surface; and (V) an adaxial series of 7 bundles that show an inverse orientation to those bundles in series I–IV. Larger bundles are collateral, with a protoxylem lacuna encircled by a ring of 9 – 14 thin-walled parenchyma cells, a relatively well-developed phloem strand, and one to three thin-walled metaxylem elements. Based on bundle arrangement, orientation, and morphology, the fossil petiole most closely resembles those of the Butomaceae and Alismataceae. This new species, Heleophyton helobiaeoides Erwin and Stockey gen. et sp.nov., in the Princeton chert flora, documents the presence of the Alismataceae in the Middle Eocene of western North America and provides further evidence that the locality represents an ancient aquatic ecosystem.