The difference between the untreated and treated pollen is quite striking. Studying the hydrated larger pollen grains under the stereo also gives an idea of their gross shape and structure before studying at higher powers under the compound microscope. 110 m, single grain ca. The treated pollen under darkfield. The depth of field is less than brightfield as the iris is fully open.
All pollen grains develop initially in groups of four called tetrads.
I haven't found a database image to check yet, but the tetrahedral form of the above willowherb pollen suggests this species is one where the tetrad doesn't separate. The willowherb species below has separate pollen grains. The same pollen under darkfield illumination. The pollen did look a blue green when collected. Pollen grains present a variety of challenges to study and interpret under the microscope.