The plant of San José, called early flower ( Primula vulgaris), has long worried botanists. It is homostile and self-pollinates, that is, the flowers always have needles of flowers of the same size and pollinates. As the presence of insects is not necessary for pollination, its diffusion is very reduced.
A group of British researchers from Milton Keynes University have discovered the reason that this flower expands so little. Fertilization is an obstacle to this flower. Due to its prosperity, San José is more pollinated by insects than conventional flowers. However, pollen grains are much smaller and of low quality, so they have little chance of germinating.