One method for the estimation of absolute pollen frequencies involves the addition of a known amount of an exotic pollen to a known quantity of sediment. From the observed ratio of indigenous to exotic pollen, the absolute quantity of indigenous per unit volume of sediment can be calculated.
The pollen of Nyssa sylvatica was considered to be a suitable exotic for addition to northwestern European Post-glacial sediments to be measured by this method. A series of experiments was made to estimate the settling rate of fresh N. sylvatica pollen in pure glycerine, to determine the period of agitation required to produce an even suspension of N. sylvatica pollen in pure glycerine, to observe the effects of KOH treatment and acetolysis on a mixture of fresh N. sylvatica and Ailanthus eligantissima pollen and to estimate the experimental error of the method by using it to determine the quantity of pollen in a series of homogenized samples of gyttja.
The value of the method for the estimation of absolute pollen frequencies is assessed.