Figure 4. Cumulative nucleus spectra for pollen (Betula pendula) suspensions containing whole grains (blue symbols), 0.2 μm filtered suspensions (orange) and 1000 kDa filtered suspensions (black).

The intial concentrations used to prepare the solutions was 2 wt. %. To examine nucleation at temperatures lower than achievable at this concentration, the suspensions were serially diluted. For the unfiltered data, data with a dilution factor of 10⁴ or greater are shown with open symbols to indicate where the expectation value for the number of grains per droplet drops below zero, and only species smaller than whole grains remain in suspension. Values are normalized to the original mass of pollen used. Most of the activity in the parent (unfiltered) suspension can be seen to remain after 0.2 μm filtration and ultrafiltration to 1000 kDa.