The features of five grass pollen seasons from two areas of contrasting climate were investigated and the relative importance of the variables controlling daily variations were determined. The records from London, UK (temperate maritime climate) and Cdrdoba, Spain (mediternnean climate) were analysed in relation to meteorological factors. The length of the seasons differs a great deal between the two locations and from year to year. However the total cumulative catches and the number of days with counts over 50 grains metreJ are similar for the two locations. Regression analysis of standardised daily avenge pollen counts shows clearly that for London, maximum and average temperatures are the most important factors influencing daily variation. In the case of C6rdoba this relationship holds true for the period from the start of the season until the peak count, but after this the relationship becomes negative. Hours of sunshine and humidity are also important. The negative effect of increased humidity on pollen release is most marked in the data for C6rdoba but it is also apparent in the case of London. The results emphasise the need for individual analysis in different climates and the application of different statistical treatments depending on the operation of the variables.

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Potential pollen production, viability and germination were studied in the most important species of Quercus in the mountains of Có rdoba to determine the contribution of each species to the total amount of airborne pollen. The results were compared over two consecutive years with different rainfall patterns. The viability of pollen grains was determined at anther opening, and during the pollination period, in order to determine potential pollination capacity. Results indicated that there were differences in the number of pollen grains produced by stamen in the four species. Equally, there were differences in the number of flowers among the species, being Q. suber the species with higher number of catkins groups and flowers per individual tree. Total pollen production per tree can be summarized in the following proportion: 1: 3: 3: 6 (Q. coccifera, Q. ilex ssp. ballota, Q. faginea and Q. suber). Potential pollen viability was estimated using the Fluorochromatic Reaction (FCR) and a germination assay. The results have shown that Quercus potential pollen viability is high and declines slowly with time. Q. coccifera was the species with the highest percentage of germination, with Q. suber being the lowest.