Does anyone know of any work relating pollen size to the efficiency of
transfer by bees? - or any other insects.  I am not particularly
interested in the known correlations between pollinator size and pollen
size, style length, stigma depth, flower size etc.  (although these may
be of interest if I have not seen them before), what I am after is
results of experimental studies.  Is there any evidence that plants are
better off with large grains than small grains when pollinated by bees -
or vice versa? (leaving aside complications of buzz pollination)
 
    William Kirk      Keele University, UK.