This is an announcement for the paper “On weakly sequentially complete Banach spaces” by E. M. Bednarczuk and K. Lesniewski. Abstract: We provide sufficient conditions for a Banach space $Y$ to be weakly sequentially complete. These conditions are expressed in terms of the existence of directional derivatives for cone convex mappings with values in $Y$. The paper may be downloaded from the archive by web browser from URL http://arxiv.org/abs/1602.04718