Floral nectar secretion and ploidy in Brassica rapa and B napus (Brassicaceae). I. Nectary size and nectar carbohydrate production and composition A. R. Davis, V. K. Sawhney, L. C. Fowke and N. H. LowApidologie, 25 6 (1994) 602-614DOI: https://doi.org/10.1051/apido:19940611