STUDIES ON POLLEN MORPHOLOGY OF ROSACEAE IN CANADA

Pollen grains of all genera of Rosaceae surveyed in Canada occur as radially symmetric isopolar monads. Many are tricolporate (rarely tricolpate), except some Sanguisorba species which are hexacolporate. Ectoapertures are slits, mostly constricted at the equator by arching sexinal pore flaps or, less often, an equatorial bridge. Alchemilla, Dalibarda, Dryas, Oemleria, Sorbaria and some Rubus species have reduced or no pore flaps. Fusiform colpus opercula occur in Chamaerhodos, Fragaria, Potentilla, Rosa, Sanguisorba and Sibbaldia. Endoapertures consist of oval to "x" or dumbell-shaped lalongate openings in the nexine. Weakly to well-developed pore chambers occur in most genera. Sculpturing of parallel ridges and valleys containing perforations predominates. Perforations are of two types, suggesting distinct evolutionary lines. They are (1) large and often extending onto tectal ridges (Amelanchier, Crataegus, Dalibarda, Dryas, Gillenia, Holodiscus, Luetkea, Physocarpus, Prunus, Pyrus, Rosa, Rubus, Sorbus, Spiraea); (2) minute pinholes (Aruncus, Fragaria, Geum, Potentilla, Sibbaldia). Other ridge-and-valley patterns include those perpendicular to the colpus (Agrimonia), intersecting (Chamaerhodos) and mixed (Oemleria, Sorbaria). Pollen with smooth (Cotoneaster, Rubus), verrucate (Rubus, Sanguisorba) and irregular (Purshia) sculpturing with pores and smooth (Alchemilla) and verrucate (Filipendula) sculpturing without pores also occur. © 1990.