"That is just what I wanted you to notice," replied his governess, "for the flowers are of two kinds, one bearing the stamens, and the other the pistils. The flowers that bear the stamens grow on loose scaly catkins, as you may see in this branch. Those with the pistils are also in catkins, but very small, like a bud. The bud spreads into a little branchlet and bears the flowers at the tip. The calyx is not seen at first; it is a mere membrane covering the ovary. By degrees the ovary swells into the acorn and the membrane becomes part of the shell."