THE VARIABILITY IN SETTLING VELOCITIES OF SOME POLLEN AND SPORES

The settling Velocity in still air of natural and dyed spores and poll en of several species was measured using the method of McCubbin and wa s found to be as follows (in cm s(-1)): black spruce (Picea mariana), 3.19; jack pine (Finns banksiana), 2.53; Lycopodium, 2.31; dyed Lycopo dium, 2.15; oil palm (Elaeis guineensis), 3.00; dyed oil palm, 2.16 an d corn(Zea Mays), 30.95. The percentage of clustered spores and pollen was taken into account but was not found to significantly affect sett ling velocity except in the case of dyed oil palm. Comparisons of the measured settling velocities of clustred grains were made with the mod el of Ferrandino and Aylor. This was found to be accurate in general, but tended to over-estimate the settling velocity of clumped spores of Lycopodium and of dyed pollen of oil palm.