Of course, if the stamens shed their pollen before the stigma is ready to receive it, or after the stigma has withered, the only possible kind of pollination is cross-pollination. These flowers must be helped by wind or insects.
In some plants the pistils and stamens grow in two different kinds of flowers. These may occur on the same plant, as in the corn and the begonia, or on different plants, as in the willow and some kinds of holly.
In corn, the flowers having stamens form the tassel at the top of the plant, and the flowers with the pistil form the ear farther down the stalk. Each pistil late flower has a few scaly bracts (a leaf from which the flower arises) and one pistil. The young corn kernel is the ovary of the pistil, and the silk is the style and stigma.
When the anthers of the staminate flowers are shedding pollen, the silks of the pistil late flowers project from the husks of the ear and receive the pollen.