Here are some images of the crushed stigmas and the pollen grains on it. Searching for literature, the only images of S. canadensis pollen grains was presented in Pellatt et al 2002 (see Figure 4).
Female stigma with pollen grains.
Image of pollen grains enlarged. The length of one pollen grain is about 37 micrometers. Photo taken with Nikon Coolpix S4100 through the light microscope.
Beattie, A.J. 1971. A technique for the study of insect-borne pollen. Pan-Pacific Entomologist. 47:82.
Pellatt, M.G., Mathewes, R.W., and Clague, J.J. 2002. Implications of a late-glacial pollen record for the glacial and climatic history of the Fraser Lowland, British Columbia. Palaeogeography, Palaeoclimatology, Palaeoecology. 180: 147-157. Link.