Hypericum majus (A. Gray) Britton is an alien species for Europe. It originates from North America and, in recent years, has been spreading in Europe. Presently, this species is found in Germany, France, Italy, Bosnia and Herzegovina, and Belarus. In Poland, it was noted for the first time in 2017 in western part of the country. Thus far, no detailed morphology and anatomy of H. majus seeds based on light and electron microscopy studies has been presented. Considering the fact that seeds provide important taxonomical information and the discussed species has not been investigated in this respect, in this research, an attemptwas made to broaden the present knowledge.
Investigations were conducted based on samples originating from three localities in Central Europe (Poland). The obtained results showed that H. majus seeds are very small – about 0.5 mm in length. In the SEM image, their surfaceis reticulate, typical of majority of species in this genus. Anatomical analysis showed that seed coat of matured seeds is very delicate, composed of two cell layers with strongly lignified walls.