Variability of Quercus robur L.

in the region of the Pomeranian plains Abstract: The results of measurements of 5780 acorns confirm that Quercus robur has acorns of langer size, as componed with acorns of Quercus petraea. Their length varied from 1.90 to 3.50 cm, with the average 2.71 cm, while in case of Q. petraea this characteristic varied from 1.60 to 3.50 cm, with the average 2.43 cm. The diam-eter of acorns was similar for both species. Dry mass of Q. robur acorns ranged from 1.054 to 4.937 g, on aver-age 2.5924 g; in the case of Q. petraea it ranged from 0.835 to 4.796 g, on average 1.8364 g. Taking into consid-eration the coefficient of variability of length and diameter, both species do not differ significantly. It ranged from 9 to 12%. In the case of dry mass the difference was larger and it was 23 % and 28 % for Q. robur and Q. petraea, respectively. The analysis of variance (F-test) showed, that the species taken as the source of variabil-ity influences significantly the length of acorns (in 17%) and dry mass (in 47%). Internal features determine these characteristics in 52 % and 46%. F-test did not detect any dependence between oak species and the di-ameter of acorns. Additional key words: oak, acorn length, acorn diameter, dry mas