Pollen grains of 12 species of western Canadian rosaceous genera, Luetkea, Oemleria, Physocarpus, and Prunus, were studied in the light microscope and scanning electron microscope. All pollen grains are produced as isopolar, radially symmetrical, usually tricolporate monads. Grains are predominantly spheroidal with a circular to triangular amb. Most of the species exhibit a well-developed chambered aperture complex at the equator, formed by a pair of sexinal flaps whereas in Prunus spinosa, Prunus americana, and Prunus virginiana the chamber is absent or weakly developed. Oemleria cerasiformis has no pore flaps. Apertures of Prunus emarginata and Prunus virginiana often have an equatorial bridge over the aperture complex. The exine of Prunus, Physocarpus, and Luetkea pollen is tectate perforate, like that of many Rosaceae. Sculpturing consists of ridges and valleys that form a striate to rugulate pattern. Ridges and valleys tend to be mainly parallel to the colpus but often loop near the poles. Pollen grains of Prunus spinosa are always rugulate or vermiculate with ridges arranged randomly. Oemleria cerasiformis pollen appears tectate imperforate. Ridges and valleys intersect at triple points in the subpolar region and curve in a semicircle around the pore area. On this basis Oemleria pollen is distinct from all other western Canadian Rosaceae. Pollen grain size ranges from small for Luetkea pectinata (17 μm in diameter) to medium for Prunus spinosa (36 × 33 μm). Key words: pollen morphology, Rosaceae, Western Canada, systematics.
Pollen tube branching in the ovary of five species of Oenothera
