INVESTIGATION ON THE MORPHOLOGICAL DISTINCTION BETWEEN THE FRUITS OF PEDUNCULATE AND SESSILE OAK

The aim of the above investigation was to find out, whether it is possible to distinguish the acorns of pedunculate and sessile oak (Quercus robur L. and Q. petraea [Matt.] Liebl.) using fruit size, shape and presence of stripes on the pericarp. None of the above features is suitable for certain identification. Statistical analyses of variance (N = 1506 acorns) of five variables characterizing size and shape showed that there is a wide intraspecific variation. The difference between the mean values of the two species is significant in four out of five cases, but surprisingly small. On the average acorns of pedunculate oak are longer and wider and generally of a more cylindrical shape than the rather ovoid fruits of sessile oak. By using several features simultaneously only 64% of the acorns were identified correctly. Presence and intensity of stripes on the pericarp turned out to be a better feature than size and shape. Distinct stripes were present in 88% of the fruits of pedunculate oak, and totally absent in 72% of those of sessile oak. 20% of all acorns showed indistinct stripes (pedunculate oak 12%, and sessile oak 28%). Allocation of indistinctly striped fruit to sessile oak results in an identification success rate of 88 to 100% depending on species composition. The practical implications of these results are discussed.